strengths of case study research method

10 Case Study Advantages and Disadvantages

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A case study in academic research is a detailed and in-depth examination of a specific instance or event, generally conducted through a qualitative approach to data.

The most common case study definition that I come across is is Robert K. Yin’s (2003, p. 13) quote provided below:

“An empirical inquiry that investigates a contemporary phenomenon within its real-life context, especially when the boundaries between phenomenon and context are not clearly evident.”

Researchers conduct case studies for a number of reasons, such as to explore complex phenomena within their real-life context, to look at a particularly interesting instance of a situation, or to dig deeper into something of interest identified in a wider-scale project.

While case studies render extremely interesting data, they have many limitations and are not suitable for all studies. One key limitation is that a case study’s findings are not usually generalizable to broader populations because one instance cannot be used to infer trends across populations.

Case Study Advantages and Disadvantages

1. in-depth analysis of complex phenomena.

Case study design allows researchers to delve deeply into intricate issues and situations.

By focusing on a specific instance or event, researchers can uncover nuanced details and layers of understanding that might be missed with other research methods, especially large-scale survey studies.

As Lee and Saunders (2017) argue,

“It allows that particular event to be studies in detail so that its unique qualities may be identified.”

This depth of analysis can provide rich insights into the underlying factors and dynamics of the studied phenomenon.

2. Holistic Understanding

Building on the above point, case studies can help us to understand a topic holistically and from multiple angles.

This means the researcher isn’t restricted to just examining a topic by using a pre-determined set of questions, as with questionnaires. Instead, researchers can use qualitative methods to delve into the many different angles, perspectives, and contextual factors related to the case study.

We can turn to Lee and Saunders (2017) again, who notes that case study researchers “develop a deep, holistic understanding of a particular phenomenon” with the intent of deeply understanding the phenomenon.

3. Examination of rare and Unusual Phenomena

We need to use case study methods when we stumble upon “rare and unusual” (Lee & Saunders, 2017) phenomena that would tend to be seen as mere outliers in population studies.

Take, for example, a child genius. A population study of all children of that child’s age would merely see this child as an outlier in the dataset, and this child may even be removed in order to predict overall trends.

So, to truly come to an understanding of this child and get insights into the environmental conditions that led to this child’s remarkable cognitive development, we need to do an in-depth study of this child specifically – so, we’d use a case study.

4. Helps Reveal the Experiences of Marginalzied Groups

Just as rare and unsual cases can be overlooked in population studies, so too can the experiences, beliefs, and perspectives of marginalized groups.

As Lee and Saunders (2017) argue, “case studies are also extremely useful in helping the expression of the voices of people whose interests are often ignored.”

Take, for example, the experiences of minority populations as they navigate healthcare systems. This was for many years a “hidden” phenomenon, not examined by researchers. It took case study designs to truly reveal this phenomenon, which helped to raise practitioners’ awareness of the importance of cultural sensitivity in medicine.

5. Ideal in Situations where Researchers cannot Control the Variables

Experimental designs – where a study takes place in a lab or controlled environment – are excellent for determining cause and effect . But not all studies can take place in controlled environments (Tetnowski, 2015).

When we’re out in the field doing observational studies or similar fieldwork, we don’t have the freedom to isolate dependent and independent variables. We need to use alternate methods.

Case studies are ideal in such situations.

A case study design will allow researchers to deeply immerse themselves in a setting (potentially combining it with methods such as ethnography or researcher observation) in order to see how phenomena take place in real-life settings.

6. Supports the generation of new theories or hypotheses

While large-scale quantitative studies such as cross-sectional designs and population surveys are excellent at testing theories and hypotheses on a large scale, they need a hypothesis to start off with!

This is where case studies – in the form of grounded research – come in. Often, a case study doesn’t start with a hypothesis. Instead, it ends with a hypothesis based upon the findings within a singular setting.

The deep analysis allows for hypotheses to emerge, which can then be taken to larger-scale studies in order to conduct further, more generalizable, testing of the hypothesis or theory.

7. Reveals the Unexpected

When a largescale quantitative research project has a clear hypothesis that it will test, it often becomes very rigid and has tunnel-vision on just exploring the hypothesis.

Of course, a structured scientific examination of the effects of specific interventions targeted at specific variables is extermely valuable.

But narrowly-focused studies often fail to shine a spotlight on unexpected and emergent data. Here, case studies come in very useful. Oftentimes, researchers set their eyes on a phenomenon and, when examining it closely with case studies, identify data and come to conclusions that are unprecedented, unforeseen, and outright surprising.

As Lars Meier (2009, p. 975) marvels, “where else can we become a part of foreign social worlds and have the chance to become aware of the unexpected?”

Disadvantages

1. not usually generalizable.

Case studies are not generalizable because they tend not to look at a broad enough corpus of data to be able to infer that there is a trend across a population.

As Yang (2022) argues, “by definition, case studies can make no claims to be typical.”

Case studies focus on one specific instance of a phenomenon. They explore the context, nuances, and situational factors that have come to bear on the case study. This is really useful for bringing to light important, new, and surprising information, as I’ve already covered.

But , it’s not often useful for generating data that has validity beyond the specific case study being examined.

2. Subjectivity in interpretation

Case studies usually (but not always) use qualitative data which helps to get deep into a topic and explain it in human terms, finding insights unattainable by quantitative data.

But qualitative data in case studies relies heavily on researcher interpretation. While researchers can be trained and work hard to focus on minimizing subjectivity (through methods like triangulation), it often emerges – some might argue it’s innevitable in qualitative studies.

So, a criticism of case studies could be that they’re more prone to subjectivity – and researchers need to take strides to address this in their studies.

3. Difficulty in replicating results

Case study research is often non-replicable because the study takes place in complex real-world settings where variables are not controlled.

So, when returning to a setting to re-do or attempt to replicate a study, we often find that the variables have changed to such an extent that replication is difficult. Furthermore, new researchers (with new subjective eyes) may catch things that the other readers overlooked.

Replication is even harder when researchers attempt to replicate a case study design in a new setting or with different participants.

Comprehension Quiz for Students

Question 1: What benefit do case studies offer when exploring the experiences of marginalized groups?

a) They provide generalizable data. b) They help express the voices of often-ignored individuals. c) They control all variables for the study. d) They always start with a clear hypothesis.

Question 2: Why might case studies be considered ideal for situations where researchers cannot control all variables?

a) They provide a structured scientific examination. b) They allow for generalizability across populations. c) They focus on one specific instance of a phenomenon. d) They allow for deep immersion in real-life settings.

Question 3: What is a primary disadvantage of case studies in terms of data applicability?

a) They always focus on the unexpected. b) They are not usually generalizable. c) They support the generation of new theories. d) They provide a holistic understanding.

Question 4: Why might case studies be considered more prone to subjectivity?

a) They always use quantitative data. b) They heavily rely on researcher interpretation, especially with qualitative data. c) They are always replicable. d) They look at a broad corpus of data.

Question 5: In what situations are experimental designs, such as those conducted in labs, most valuable?

a) When there’s a need to study rare and unusual phenomena. b) When a holistic understanding is required. c) When determining cause-and-effect relationships. d) When the study focuses on marginalized groups.

Question 6: Why is replication challenging in case study research?

a) Because they always use qualitative data. b) Because they tend to focus on a broad corpus of data. c) Due to the changing variables in complex real-world settings. d) Because they always start with a hypothesis.

Lee, B., & Saunders, M. N. K. (2017). Conducting Case Study Research for Business and Management Students. SAGE Publications.

Meir, L. (2009). Feasting on the Benefits of Case Study Research. In Mills, A. J., Wiebe, E., & Durepos, G. (Eds.). Encyclopedia of Case Study Research (Vol. 2). London: SAGE Publications.

Tetnowski, J. (2015). Qualitative case study research design.  Perspectives on fluency and fluency disorders ,  25 (1), 39-45. ( Source )

Yang, S. L. (2022). The War on Corruption in China: Local Reform and Innovation . Taylor & Francis.

Yin, R. (2003). Case Study research. Thousand Oaks, CA: Sage.

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• What Is a Case Study? | Definition, Examples & Methods

What Is a Case Study? | Definition, Examples & Methods

Published on May 8, 2019 by Shona McCombes . Revised on November 20, 2023.

A case study is a detailed study of a specific subject, such as a person, group, place, event, organization, or phenomenon. Case studies are commonly used in social, educational, clinical, and business research.

A case study research design usually involves qualitative methods , but quantitative methods are sometimes also used. Case studies are good for describing , comparing, evaluating and understanding different aspects of a research problem .

Table of contents

When to do a case study, step 1: select a case, step 2: build a theoretical framework, step 3: collect your data, step 4: describe and analyze the case, other interesting articles.

A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject. It allows you to explore the key characteristics, meanings, and implications of the case.

Case studies are often a good choice in a thesis or dissertation . They keep your project focused and manageable when you don’t have the time or resources to do large-scale research.

You might use just one complex case study where you explore a single subject in depth, or conduct multiple case studies to compare and illuminate different aspects of your research problem.

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Once you have developed your problem statement and research questions , you should be ready to choose the specific case that you want to focus on. A good case study should have the potential to:

• Provide new or unexpected insights into the subject
• Challenge or complicate existing assumptions and theories
• Propose practical courses of action to resolve a problem
• Open up new directions for future research

TipIf your research is more practical in nature and aims to simultaneously investigate an issue as you solve it, consider conducting action research instead.

Unlike quantitative or experimental research , a strong case study does not require a random or representative sample. In fact, case studies often deliberately focus on unusual, neglected, or outlying cases which may shed new light on the research problem.

Example of an outlying case studyIn the 1960s the town of Roseto, Pennsylvania was discovered to have extremely low rates of heart disease compared to the US average. It became an important case study for understanding previously neglected causes of heart disease.

However, you can also choose a more common or representative case to exemplify a particular category, experience or phenomenon.

Example of a representative case studyIn the 1920s, two sociologists used Muncie, Indiana as a case study of a typical American city that supposedly exemplified the changing culture of the US at the time.

While case studies focus more on concrete details than general theories, they should usually have some connection with theory in the field. This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to:

• Exemplify a theory by showing how it explains the case under investigation
• Expand on a theory by uncovering new concepts and ideas that need to be incorporated
• Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions

To ensure that your analysis of the case has a solid academic grounding, you should conduct a literature review of sources related to the topic and develop a theoretical framework . This means identifying key concepts and theories to guide your analysis and interpretation.

There are many different research methods you can use to collect data on your subject. Case studies tend to focus on qualitative data using methods such as interviews , observations , and analysis of primary and secondary sources (e.g., newspaper articles, photographs, official records). Sometimes a case study will also collect quantitative data.

Example of a mixed methods case studyFor a case study of a wind farm development in a rural area, you could collect quantitative data on employment rates and business revenue, collect qualitative data on local people’s perceptions and experiences, and analyze local and national media coverage of the development.

The aim is to gain as thorough an understanding as possible of the case and its context.

In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject.

How you report your findings depends on the type of research you are doing. Some case studies are structured like a standard scientific paper or thesis , with separate sections or chapters for the methods , results and discussion .

Others are written in a more narrative style, aiming to explore the case from various angles and analyze its meanings and implications (for example, by using textual analysis or discourse analysis ).

In all cases, though, make sure to give contextual details about the case, connect it back to the literature and theory, and discuss how it fits into wider patterns or debates.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

• Normal distribution
• Degrees of freedom
• Null hypothesis
• Discourse analysis
• Control groups
• Mixed methods research
• Non-probability sampling
• Quantitative research
• Ecological validity

Research bias

• Rosenthal effect
• Implicit bias
• Cognitive bias
• Selection bias
• Negativity bias
• Status quo bias

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The Ultimate Guide to Qualitative Research - Part 1: The Basics

• Introduction and overview
• What is qualitative research?
• What is qualitative data?
• Examples of qualitative data
• Qualitative vs. quantitative research
• Mixed methods
• Qualitative research preparation
• Theoretical perspective
• Theoretical framework
• Literature reviews

Research question

• Conceptual framework
• Conceptual vs. theoretical framework

Data collection

• Qualitative research methods
• Focus groups
• Observational research

What is a case study?

Applications for case study research, what is a good case study, process of case study design, benefits and limitations of case studies.

• Ethnographical research
• Ethical considerations
• Confidentiality and privacy
• Power dynamics
• Reflexivity

Case studies

Case studies are essential to qualitative research , offering a lens through which researchers can investigate complex phenomena within their real-life contexts. This chapter explores the concept, purpose, applications, examples, and types of case studies and provides guidance on how to conduct case study research effectively.

Whereas quantitative methods look at phenomena at scale, case study research looks at a concept or phenomenon in considerable detail. While analyzing a single case can help understand one perspective regarding the object of research inquiry, analyzing multiple cases can help obtain a more holistic sense of the topic or issue. Let's provide a basic definition of a case study, then explore its characteristics and role in the qualitative research process.

Definition of a case study

A case study in qualitative research is a strategy of inquiry that involves an in-depth investigation of a phenomenon within its real-world context. It provides researchers with the opportunity to acquire an in-depth understanding of intricate details that might not be as apparent or accessible through other methods of research. The specific case or cases being studied can be a single person, group, or organization – demarcating what constitutes a relevant case worth studying depends on the researcher and their research question .

Among qualitative research methods , a case study relies on multiple sources of evidence, such as documents, artifacts, interviews , or observations , to present a complete and nuanced understanding of the phenomenon under investigation. The objective is to illuminate the readers' understanding of the phenomenon beyond its abstract statistical or theoretical explanations.

Characteristics of case studies

Case studies typically possess a number of distinct characteristics that set them apart from other research methods. These characteristics include a focus on holistic description and explanation, flexibility in the design and data collection methods, reliance on multiple sources of evidence, and emphasis on the context in which the phenomenon occurs.

Furthermore, case studies can often involve a longitudinal examination of the case, meaning they study the case over a period of time. These characteristics allow case studies to yield comprehensive, in-depth, and richly contextualized insights about the phenomenon of interest.

The role of case studies in research

Case studies hold a unique position in the broader landscape of research methods aimed at theory development. They are instrumental when the primary research interest is to gain an intensive, detailed understanding of a phenomenon in its real-life context.

In addition, case studies can serve different purposes within research - they can be used for exploratory, descriptive, or explanatory purposes, depending on the research question and objectives. This flexibility and depth make case studies a valuable tool in the toolkit of qualitative researchers.

Remember, a well-conducted case study can offer a rich, insightful contribution to both academic and practical knowledge through theory development or theory verification, thus enhancing our understanding of complex phenomena in their real-world contexts.

What is the purpose of a case study?

Case study research aims for a more comprehensive understanding of phenomena, requiring various research methods to gather information for qualitative analysis . Ultimately, a case study can allow the researcher to gain insight into a particular object of inquiry and develop a theoretical framework relevant to the research inquiry.

Why use case studies in qualitative research?

Using case studies as a research strategy depends mainly on the nature of the research question and the researcher's access to the data.

Conducting case study research provides a level of detail and contextual richness that other research methods might not offer. They are beneficial when there's a need to understand complex social phenomena within their natural contexts.

The explanatory, exploratory, and descriptive roles of case studies

Case studies can take on various roles depending on the research objectives. They can be exploratory when the research aims to discover new phenomena or define new research questions; they are descriptive when the objective is to depict a phenomenon within its context in a detailed manner; and they can be explanatory if the goal is to understand specific relationships within the studied context. Thus, the versatility of case studies allows researchers to approach their topic from different angles, offering multiple ways to uncover and interpret the data .

The impact of case studies on knowledge development

Case studies play a significant role in knowledge development across various disciplines. Analysis of cases provides an avenue for researchers to explore phenomena within their context based on the collected data.

This can result in the production of rich, practical insights that can be instrumental in both theory-building and practice. Case studies allow researchers to delve into the intricacies and complexities of real-life situations, uncovering insights that might otherwise remain hidden.

Types of case studies

In qualitative research , a case study is not a one-size-fits-all approach. Depending on the nature of the research question and the specific objectives of the study, researchers might choose to use different types of case studies. These types differ in their focus, methodology, and the level of detail they provide about the phenomenon under investigation.

Understanding these types is crucial for selecting the most appropriate approach for your research project and effectively achieving your research goals. Let's briefly look at the main types of case studies.

Exploratory case studies

Exploratory case studies are typically conducted to develop a theory or framework around an understudied phenomenon. They can also serve as a precursor to a larger-scale research project. Exploratory case studies are useful when a researcher wants to identify the key issues or questions which can spur more extensive study or be used to develop propositions for further research. These case studies are characterized by flexibility, allowing researchers to explore various aspects of a phenomenon as they emerge, which can also form the foundation for subsequent studies.

Descriptive case studies

Descriptive case studies aim to provide a complete and accurate representation of a phenomenon or event within its context. These case studies are often based on an established theoretical framework, which guides how data is collected and analyzed. The researcher is concerned with describing the phenomenon in detail, as it occurs naturally, without trying to influence or manipulate it.

Explanatory case studies

Explanatory case studies are focused on explanation - they seek to clarify how or why certain phenomena occur. Often used in complex, real-life situations, they can be particularly valuable in clarifying causal relationships among concepts and understanding the interplay between different factors within a specific context.

Intrinsic, instrumental, and collective case studies

These three categories of case studies focus on the nature and purpose of the study. An intrinsic case study is conducted when a researcher has an inherent interest in the case itself. Instrumental case studies are employed when the case is used to provide insight into a particular issue or phenomenon. A collective case study, on the other hand, involves studying multiple cases simultaneously to investigate some general phenomena.

Each type of case study serves a different purpose and has its own strengths and challenges. The selection of the type should be guided by the research question and objectives, as well as the context and constraints of the research.

The flexibility, depth, and contextual richness offered by case studies make this approach an excellent research method for various fields of study. They enable researchers to investigate real-world phenomena within their specific contexts, capturing nuances that other research methods might miss. Across numerous fields, case studies provide valuable insights into complex issues.

Critical information systems research

Case studies provide a detailed understanding of the role and impact of information systems in different contexts. They offer a platform to explore how information systems are designed, implemented, and used and how they interact with various social, economic, and political factors. Case studies in this field often focus on examining the intricate relationship between technology, organizational processes, and user behavior, helping to uncover insights that can inform better system design and implementation.

Health research

Health research is another field where case studies are highly valuable. They offer a way to explore patient experiences, healthcare delivery processes, and the impact of various interventions in a real-world context.

Case studies can provide a deep understanding of a patient's journey, giving insights into the intricacies of disease progression, treatment effects, and the psychosocial aspects of health and illness.

Asthma research studies

Specifically within medical research, studies on asthma often employ case studies to explore the individual and environmental factors that influence asthma development, management, and outcomes. A case study can provide rich, detailed data about individual patients' experiences, from the triggers and symptoms they experience to the effectiveness of various management strategies. This can be crucial for developing patient-centered asthma care approaches.

Other fields

Apart from the fields mentioned, case studies are also extensively used in business and management research, education research, and political sciences, among many others. They provide an opportunity to delve into the intricacies of real-world situations, allowing for a comprehensive understanding of various phenomena.

Case studies, with their depth and contextual focus, offer unique insights across these varied fields. They allow researchers to illuminate the complexities of real-life situations, contributing to both theory and practice.

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Understanding the key elements of case study design is crucial for conducting rigorous and impactful case study research. A well-structured design guides the researcher through the process, ensuring that the study is methodologically sound and its findings are reliable and valid. The main elements of case study design include the research question , propositions, units of analysis, and the logic linking the data to the propositions.

The research question is the foundation of any research study. A good research question guides the direction of the study and informs the selection of the case, the methods of collecting data, and the analysis techniques. A well-formulated research question in case study research is typically clear, focused, and complex enough to merit further detailed examination of the relevant case(s).

Propositions

Propositions, though not necessary in every case study, provide a direction by stating what we might expect to find in the data collected. They guide how data is collected and analyzed by helping researchers focus on specific aspects of the case. They are particularly important in explanatory case studies, which seek to understand the relationships among concepts within the studied phenomenon.

Units of analysis

The unit of analysis refers to the case, or the main entity or entities that are being analyzed in the study. In case study research, the unit of analysis can be an individual, a group, an organization, a decision, an event, or even a time period. It's crucial to clearly define the unit of analysis, as it shapes the qualitative data analysis process by allowing the researcher to analyze a particular case and synthesize analysis across multiple case studies to draw conclusions.

Argumentation

This refers to the inferential model that allows researchers to draw conclusions from the data. The researcher needs to ensure that there is a clear link between the data, the propositions (if any), and the conclusions drawn. This argumentation is what enables the researcher to make valid and credible inferences about the phenomenon under study.

Understanding and carefully considering these elements in the design phase of a case study can significantly enhance the quality of the research. It can help ensure that the study is methodologically sound and its findings contribute meaningful insights about the case.

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Conducting a case study involves several steps, from defining the research question and selecting the case to collecting and analyzing data . This section outlines these key stages, providing a practical guide on how to conduct case study research.

Defining the research question

The first step in case study research is defining a clear, focused research question. This question should guide the entire research process, from case selection to analysis. It's crucial to ensure that the research question is suitable for a case study approach. Typically, such questions are exploratory or descriptive in nature and focus on understanding a phenomenon within its real-life context.

Selecting and defining the case

The selection of the case should be based on the research question and the objectives of the study. It involves choosing a unique example or a set of examples that provide rich, in-depth data about the phenomenon under investigation. After selecting the case, it's crucial to define it clearly, setting the boundaries of the case, including the time period and the specific context.

Previous research can help guide the case study design. When considering a case study, an example of a case could be taken from previous case study research and used to define cases in a new research inquiry. Considering recently published examples can help understand how to select and define cases effectively.

Developing a detailed case study protocol

A case study protocol outlines the procedures and general rules to be followed during the case study. This includes the data collection methods to be used, the sources of data, and the procedures for analysis. Having a detailed case study protocol ensures consistency and reliability in the study.

The protocol should also consider how to work with the people involved in the research context to grant the research team access to collecting data. As mentioned in previous sections of this guide, establishing rapport is an essential component of qualitative research as it shapes the overall potential for collecting and analyzing data.

Collecting data

Gathering data in case study research often involves multiple sources of evidence, including documents, archival records, interviews, observations, and physical artifacts. This allows for a comprehensive understanding of the case. The process for gathering data should be systematic and carefully documented to ensure the reliability and validity of the study.

Analyzing and interpreting data

The next step is analyzing the data. This involves organizing the data , categorizing it into themes or patterns , and interpreting these patterns to answer the research question. The analysis might also involve comparing the findings with prior research or theoretical propositions.

Writing the case study report

The final step is writing the case study report . This should provide a detailed description of the case, the data, the analysis process, and the findings. The report should be clear, organized, and carefully written to ensure that the reader can understand the case and the conclusions drawn from it.

Each of these steps is crucial in ensuring that the case study research is rigorous, reliable, and provides valuable insights about the case.

The type, depth, and quality of data in your study can significantly influence the validity and utility of the study. In case study research, data is usually collected from multiple sources to provide a comprehensive and nuanced understanding of the case. This section will outline the various methods of collecting data used in case study research and discuss considerations for ensuring the quality of the data.

Interviews are a common method of gathering data in case study research. They can provide rich, in-depth data about the perspectives, experiences, and interpretations of the individuals involved in the case. Interviews can be structured , semi-structured , or unstructured , depending on the research question and the degree of flexibility needed.

Observations

Observations involve the researcher observing the case in its natural setting, providing first-hand information about the case and its context. Observations can provide data that might not be revealed in interviews or documents, such as non-verbal cues or contextual information.

Documents and artifacts

Documents and archival records provide a valuable source of data in case study research. They can include reports, letters, memos, meeting minutes, email correspondence, and various public and private documents related to the case.

These records can provide historical context, corroborate evidence from other sources, and offer insights into the case that might not be apparent from interviews or observations.

Physical artifacts refer to any physical evidence related to the case, such as tools, products, or physical environments. These artifacts can provide tangible insights into the case, complementing the data gathered from other sources.

Ensuring the quality of data collection

Determining the quality of data in case study research requires careful planning and execution. It's crucial to ensure that the data is reliable, accurate, and relevant to the research question. This involves selecting appropriate methods of collecting data, properly training interviewers or observers, and systematically recording and storing the data. It also includes considering ethical issues related to collecting and handling data, such as obtaining informed consent and ensuring the privacy and confidentiality of the participants.

Data analysis

Analyzing case study research involves making sense of the rich, detailed data to answer the research question. This process can be challenging due to the volume and complexity of case study data. However, a systematic and rigorous approach to analysis can ensure that the findings are credible and meaningful. This section outlines the main steps and considerations in analyzing data in case study research.

Organizing the data

The first step in the analysis is organizing the data. This involves sorting the data into manageable sections, often according to the data source or the theme. This step can also involve transcribing interviews, digitizing physical artifacts, or organizing observational data.

Categorizing and coding the data

Once the data is organized, the next step is to categorize or code the data. This involves identifying common themes, patterns, or concepts in the data and assigning codes to relevant data segments. Coding can be done manually or with the help of software tools, and in either case, qualitative analysis software can greatly facilitate the entire coding process. Coding helps to reduce the data to a set of themes or categories that can be more easily analyzed.

Identifying patterns and themes

After coding the data, the researcher looks for patterns or themes in the coded data. This involves comparing and contrasting the codes and looking for relationships or patterns among them. The identified patterns and themes should help answer the research question.

Interpreting the data

Once patterns and themes have been identified, the next step is to interpret these findings. This involves explaining what the patterns or themes mean in the context of the research question and the case. This interpretation should be grounded in the data, but it can also involve drawing on theoretical concepts or prior research.

Verification of the data

The last step in the analysis is verification. This involves checking the accuracy and consistency of the analysis process and confirming that the findings are supported by the data. This can involve re-checking the original data, checking the consistency of codes, or seeking feedback from research participants or peers.

Like any research method , case study research has its strengths and limitations. Researchers must be aware of these, as they can influence the design, conduct, and interpretation of the study.

Understanding the strengths and limitations of case study research can also guide researchers in deciding whether this approach is suitable for their research question . This section outlines some of the key strengths and limitations of case study research.

Benefits include the following:

• Rich, detailed data: One of the main strengths of case study research is that it can generate rich, detailed data about the case. This can provide a deep understanding of the case and its context, which can be valuable in exploring complex phenomena.
• Flexibility: Case study research is flexible in terms of design , data collection , and analysis . A sufficient degree of flexibility allows the researcher to adapt the study according to the case and the emerging findings.
• Real-world context: Case study research involves studying the case in its real-world context, which can provide valuable insights into the interplay between the case and its context.
• Multiple sources of evidence: Case study research often involves collecting data from multiple sources , which can enhance the robustness and validity of the findings.

On the other hand, researchers should consider the following limitations:

• Generalizability: A common criticism of case study research is that its findings might not be generalizable to other cases due to the specificity and uniqueness of each case.
• Time and resource intensive: Case study research can be time and resource intensive due to the depth of the investigation and the amount of collected data.
• Complexity of analysis: The rich, detailed data generated in case study research can make analyzing the data challenging.
• Subjectivity: Given the nature of case study research, there may be a higher degree of subjectivity in interpreting the data , so researchers need to reflect on this and transparently convey to audiences how the research was conducted.

Being aware of these strengths and limitations can help researchers design and conduct case study research effectively and interpret and report the findings appropriately.

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Home » Case Study – Methods, Examples and Guide

Case Study – Methods, Examples and Guide

Table of Contents

A case study is a research method that involves an in-depth examination and analysis of a particular phenomenon or case, such as an individual, organization, community, event, or situation.

It is a qualitative research approach that aims to provide a detailed and comprehensive understanding of the case being studied. Case studies typically involve multiple sources of data, including interviews, observations, documents, and artifacts, which are analyzed using various techniques, such as content analysis, thematic analysis, and grounded theory. The findings of a case study are often used to develop theories, inform policy or practice, or generate new research questions.

Types of Case Study

Types and Methods of Case Study are as follows:

Single-Case Study

A single-case study is an in-depth analysis of a single case. This type of case study is useful when the researcher wants to understand a specific phenomenon in detail.

For Example , A researcher might conduct a single-case study on a particular individual to understand their experiences with a particular health condition or a specific organization to explore their management practices. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of a single-case study are often used to generate new research questions, develop theories, or inform policy or practice.

Multiple-Case Study

A multiple-case study involves the analysis of several cases that are similar in nature. This type of case study is useful when the researcher wants to identify similarities and differences between the cases.

For Example, a researcher might conduct a multiple-case study on several companies to explore the factors that contribute to their success or failure. The researcher collects data from each case, compares and contrasts the findings, and uses various techniques to analyze the data, such as comparative analysis or pattern-matching. The findings of a multiple-case study can be used to develop theories, inform policy or practice, or generate new research questions.

Exploratory Case Study

An exploratory case study is used to explore a new or understudied phenomenon. This type of case study is useful when the researcher wants to generate hypotheses or theories about the phenomenon.

For Example, a researcher might conduct an exploratory case study on a new technology to understand its potential impact on society. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as grounded theory or content analysis. The findings of an exploratory case study can be used to generate new research questions, develop theories, or inform policy or practice.

Descriptive Case Study

A descriptive case study is used to describe a particular phenomenon in detail. This type of case study is useful when the researcher wants to provide a comprehensive account of the phenomenon.

For Example, a researcher might conduct a descriptive case study on a particular community to understand its social and economic characteristics. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of a descriptive case study can be used to inform policy or practice or generate new research questions.

Instrumental Case Study

An instrumental case study is used to understand a particular phenomenon that is instrumental in achieving a particular goal. This type of case study is useful when the researcher wants to understand the role of the phenomenon in achieving the goal.

For Example, a researcher might conduct an instrumental case study on a particular policy to understand its impact on achieving a particular goal, such as reducing poverty. The researcher collects data from multiple sources, such as interviews, observations, and documents, and uses various techniques to analyze the data, such as content analysis or thematic analysis. The findings of an instrumental case study can be used to inform policy or practice or generate new research questions.

Case Study Data Collection Methods

Here are some common data collection methods for case studies:

Interviews involve asking questions to individuals who have knowledge or experience relevant to the case study. Interviews can be structured (where the same questions are asked to all participants) or unstructured (where the interviewer follows up on the responses with further questions). Interviews can be conducted in person, over the phone, or through video conferencing.

Observations

Observations involve watching and recording the behavior and activities of individuals or groups relevant to the case study. Observations can be participant (where the researcher actively participates in the activities) or non-participant (where the researcher observes from a distance). Observations can be recorded using notes, audio or video recordings, or photographs.

Documents can be used as a source of information for case studies. Documents can include reports, memos, emails, letters, and other written materials related to the case study. Documents can be collected from the case study participants or from public sources.

Surveys involve asking a set of questions to a sample of individuals relevant to the case study. Surveys can be administered in person, over the phone, through mail or email, or online. Surveys can be used to gather information on attitudes, opinions, or behaviors related to the case study.

Artifacts are physical objects relevant to the case study. Artifacts can include tools, equipment, products, or other objects that provide insights into the case study phenomenon.

How to conduct Case Study Research

Conducting a case study research involves several steps that need to be followed to ensure the quality and rigor of the study. Here are the steps to conduct case study research:

• Define the research questions: The first step in conducting a case study research is to define the research questions. The research questions should be specific, measurable, and relevant to the case study phenomenon under investigation.
• Select the case: The next step is to select the case or cases to be studied. The case should be relevant to the research questions and should provide rich and diverse data that can be used to answer the research questions.
• Collect data: Data can be collected using various methods, such as interviews, observations, documents, surveys, and artifacts. The data collection method should be selected based on the research questions and the nature of the case study phenomenon.
• Analyze the data: The data collected from the case study should be analyzed using various techniques, such as content analysis, thematic analysis, or grounded theory. The analysis should be guided by the research questions and should aim to provide insights and conclusions relevant to the research questions.
• Draw conclusions: The conclusions drawn from the case study should be based on the data analysis and should be relevant to the research questions. The conclusions should be supported by evidence and should be clearly stated.
• Validate the findings: The findings of the case study should be validated by reviewing the data and the analysis with participants or other experts in the field. This helps to ensure the validity and reliability of the findings.
• Write the report: The final step is to write the report of the case study research. The report should provide a clear description of the case study phenomenon, the research questions, the data collection methods, the data analysis, the findings, and the conclusions. The report should be written in a clear and concise manner and should follow the guidelines for academic writing.

Examples of Case Study

Here are some examples of case study research:

• The Hawthorne Studies : Conducted between 1924 and 1932, the Hawthorne Studies were a series of case studies conducted by Elton Mayo and his colleagues to examine the impact of work environment on employee productivity. The studies were conducted at the Hawthorne Works plant of the Western Electric Company in Chicago and included interviews, observations, and experiments.
• The Stanford Prison Experiment: Conducted in 1971, the Stanford Prison Experiment was a case study conducted by Philip Zimbardo to examine the psychological effects of power and authority. The study involved simulating a prison environment and assigning participants to the role of guards or prisoners. The study was controversial due to the ethical issues it raised.
• The Challenger Disaster: The Challenger Disaster was a case study conducted to examine the causes of the Space Shuttle Challenger explosion in 1986. The study included interviews, observations, and analysis of data to identify the technical, organizational, and cultural factors that contributed to the disaster.
• The Enron Scandal: The Enron Scandal was a case study conducted to examine the causes of the Enron Corporation’s bankruptcy in 2001. The study included interviews, analysis of financial data, and review of documents to identify the accounting practices, corporate culture, and ethical issues that led to the company’s downfall.
• The Fukushima Nuclear Disaster : The Fukushima Nuclear Disaster was a case study conducted to examine the causes of the nuclear accident that occurred at the Fukushima Daiichi Nuclear Power Plant in Japan in 2011. The study included interviews, analysis of data, and review of documents to identify the technical, organizational, and cultural factors that contributed to the disaster.

Application of Case Study

Case studies have a wide range of applications across various fields and industries. Here are some examples:

Business and Management

Case studies are widely used in business and management to examine real-life situations and develop problem-solving skills. Case studies can help students and professionals to develop a deep understanding of business concepts, theories, and best practices.

Case studies are used in healthcare to examine patient care, treatment options, and outcomes. Case studies can help healthcare professionals to develop critical thinking skills, diagnose complex medical conditions, and develop effective treatment plans.

Case studies are used in education to examine teaching and learning practices. Case studies can help educators to develop effective teaching strategies, evaluate student progress, and identify areas for improvement.

Social Sciences

Case studies are widely used in social sciences to examine human behavior, social phenomena, and cultural practices. Case studies can help researchers to develop theories, test hypotheses, and gain insights into complex social issues.

Law and Ethics

Case studies are used in law and ethics to examine legal and ethical dilemmas. Case studies can help lawyers, policymakers, and ethical professionals to develop critical thinking skills, analyze complex cases, and make informed decisions.

Purpose of Case Study

The purpose of a case study is to provide a detailed analysis of a specific phenomenon, issue, or problem in its real-life context. A case study is a qualitative research method that involves the in-depth exploration and analysis of a particular case, which can be an individual, group, organization, event, or community.

The primary purpose of a case study is to generate a comprehensive and nuanced understanding of the case, including its history, context, and dynamics. Case studies can help researchers to identify and examine the underlying factors, processes, and mechanisms that contribute to the case and its outcomes. This can help to develop a more accurate and detailed understanding of the case, which can inform future research, practice, or policy.

Case studies can also serve other purposes, including:

• Illustrating a theory or concept: Case studies can be used to illustrate and explain theoretical concepts and frameworks, providing concrete examples of how they can be applied in real-life situations.
• Developing hypotheses: Case studies can help to generate hypotheses about the causal relationships between different factors and outcomes, which can be tested through further research.
• Providing insight into complex issues: Case studies can provide insights into complex and multifaceted issues, which may be difficult to understand through other research methods.
• Informing practice or policy: Case studies can be used to inform practice or policy by identifying best practices, lessons learned, or areas for improvement.

Advantages of Case Study Research

There are several advantages of case study research, including:

• In-depth exploration: Case study research allows for a detailed exploration and analysis of a specific phenomenon, issue, or problem in its real-life context. This can provide a comprehensive understanding of the case and its dynamics, which may not be possible through other research methods.
• Rich data: Case study research can generate rich and detailed data, including qualitative data such as interviews, observations, and documents. This can provide a nuanced understanding of the case and its complexity.
• Holistic perspective: Case study research allows for a holistic perspective of the case, taking into account the various factors, processes, and mechanisms that contribute to the case and its outcomes. This can help to develop a more accurate and comprehensive understanding of the case.
• Theory development: Case study research can help to develop and refine theories and concepts by providing empirical evidence and concrete examples of how they can be applied in real-life situations.
• Practical application: Case study research can inform practice or policy by identifying best practices, lessons learned, or areas for improvement.
• Contextualization: Case study research takes into account the specific context in which the case is situated, which can help to understand how the case is influenced by the social, cultural, and historical factors of its environment.

Limitations of Case Study Research

There are several limitations of case study research, including:

• Limited generalizability : Case studies are typically focused on a single case or a small number of cases, which limits the generalizability of the findings. The unique characteristics of the case may not be applicable to other contexts or populations, which may limit the external validity of the research.
• Biased sampling: Case studies may rely on purposive or convenience sampling, which can introduce bias into the sample selection process. This may limit the representativeness of the sample and the generalizability of the findings.
• Subjectivity: Case studies rely on the interpretation of the researcher, which can introduce subjectivity into the analysis. The researcher’s own biases, assumptions, and perspectives may influence the findings, which may limit the objectivity of the research.
• Limited control: Case studies are typically conducted in naturalistic settings, which limits the control that the researcher has over the environment and the variables being studied. This may limit the ability to establish causal relationships between variables.
• Time-consuming: Case studies can be time-consuming to conduct, as they typically involve a detailed exploration and analysis of a specific case. This may limit the feasibility of conducting multiple case studies or conducting case studies in a timely manner.
• Resource-intensive: Case studies may require significant resources, including time, funding, and expertise. This may limit the ability of researchers to conduct case studies in resource-constrained settings.

About the author

Muhammad Hassan

Researcher, Academic Writer, Web developer

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Case Study Research Method in Psychology

Saul Mcleod, PhD

Editor-in-Chief for Simply Psychology

BSc (Hons) Psychology, MRes, PhD, University of Manchester

Saul Mcleod, PhD., is a qualified psychology teacher with over 18 years of experience in further and higher education. He has been published in peer-reviewed journals, including the Journal of Clinical Psychology.

Learn about our Editorial Process

Olivia Guy-Evans, MSc

Associate Editor for Simply Psychology

BSc (Hons) Psychology, MSc Psychology of Education

Olivia Guy-Evans is a writer and associate editor for Simply Psychology. She has previously worked in healthcare and educational sectors.

On This Page:

Case studies are in-depth investigations of a person, group, event, or community. Typically, data is gathered from various sources using several methods (e.g., observations & interviews).

The case study research method originated in clinical medicine (the case history, i.e., the patient’s personal history). In psychology, case studies are often confined to the study of a particular individual.

The information is mainly biographical and relates to events in the individual’s past (i.e., retrospective), as well as to significant events that are currently occurring in his or her everyday life.

The case study is not a research method, but researchers select methods of data collection and analysis that will generate material suitable for case studies.

Freud (1909a, 1909b) conducted very detailed investigations into the private lives of his patients in an attempt to both understand and help them overcome their illnesses.

This makes it clear that the case study is a method that should only be used by a psychologist, therapist, or psychiatrist, i.e., someone with a professional qualification.

There is an ethical issue of competence. Only someone qualified to diagnose and treat a person can conduct a formal case study relating to atypical (i.e., abnormal) behavior or atypical development.

 Famous Case Studies

• Anna O – One of the most famous case studies, documenting psychoanalyst Josef Breuer’s treatment of “Anna O” (real name Bertha Pappenheim) for hysteria in the late 1800s using early psychoanalytic theory.
• Little Hans – A child psychoanalysis case study published by Sigmund Freud in 1909 analyzing his five-year-old patient Herbert Graf’s house phobia as related to the Oedipus complex.
• Bruce/Brenda – Gender identity case of the boy (Bruce) whose botched circumcision led psychologist John Money to advise gender reassignment and raise him as a girl (Brenda) in the 1960s.
• Genie Wiley – Linguistics/psychological development case of the victim of extreme isolation abuse who was studied in 1970s California for effects of early language deprivation on acquiring speech later in life.
• Phineas Gage – One of the most famous neuropsychology case studies analyzes personality changes in railroad worker Phineas Gage after an 1848 brain injury involving a tamping iron piercing his skull.

Clinical Case Studies

• Studying the effectiveness of psychotherapy approaches with an individual patient
• Assessing and treating mental illnesses like depression, anxiety disorders, PTSD
• Neuropsychological cases investigating brain injuries or disorders

Child Psychology Case Studies

• Studying psychological development from birth through adolescence
• Cases of learning disabilities, autism spectrum disorders, ADHD
• Effects of trauma, abuse, deprivation on development

Types of Case Studies

• Explanatory case studies : Used to explore causation in order to find underlying principles. Helpful for doing qualitative analysis to explain presumed causal links.
• Exploratory case studies : Used to explore situations where an intervention being evaluated has no clear set of outcomes. It helps define questions and hypotheses for future research.
• Descriptive case studies : Describe an intervention or phenomenon and the real-life context in which it occurred. It is helpful for illustrating certain topics within an evaluation.
• Multiple-case studies : Used to explore differences between cases and replicate findings across cases. Helpful for comparing and contrasting specific cases.
• Intrinsic : Used to gain a better understanding of a particular case. Helpful for capturing the complexity of a single case.
• Collective : Used to explore a general phenomenon using multiple case studies. Helpful for jointly studying a group of cases in order to inquire into the phenomenon.

Where Do You Find Data for a Case Study?

There are several places to find data for a case study. The key is to gather data from multiple sources to get a complete picture of the case and corroborate facts or findings through triangulation of evidence. Most of this information is likely qualitative (i.e., verbal description rather than measurement), but the psychologist might also collect numerical data.

1. Primary sources

• Interviews – Interviewing key people related to the case to get their perspectives and insights. The interview is an extremely effective procedure for obtaining information about an individual, and it may be used to collect comments from the person’s friends, parents, employer, workmates, and others who have a good knowledge of the person, as well as to obtain facts from the person him or herself.
• Observations – Observing behaviors, interactions, processes, etc., related to the case as they unfold in real-time.
• Documents & Records – Reviewing private documents, diaries, public records, correspondence, meeting minutes, etc., relevant to the case.

2. Secondary sources

• News/Media – News coverage of events related to the case study.
• Academic articles – Journal articles, dissertations etc. that discuss the case.
• Government reports – Official data and records related to the case context.
• Books/films – Books, documentaries or films discussing the case.

3. Archival records

Searching historical archives, museum collections and databases to find relevant documents, visual/audio records related to the case history and context.

Public archives like newspapers, organizational records, photographic collections could all include potentially relevant pieces of information to shed light on attitudes, cultural perspectives, common practices and historical contexts related to psychology.

4. Organizational records

Organizational records offer the advantage of often having large datasets collected over time that can reveal or confirm psychological insights.

Of course, privacy and ethical concerns regarding confidential data must be navigated carefully.

However, with proper protocols, organizational records can provide invaluable context and empirical depth to qualitative case studies exploring the intersection of psychology and organizations.

• Organizational/industrial psychology research : Organizational records like employee surveys, turnover/retention data, policies, incident reports etc. may provide insight into topics like job satisfaction, workplace culture and dynamics, leadership issues, employee behaviors etc.
• Clinical psychology : Therapists/hospitals may grant access to anonymized medical records to study aspects like assessments, diagnoses, treatment plans etc. This could shed light on clinical practices.
• School psychology : Studies could utilize anonymized student records like test scores, grades, disciplinary issues, and counseling referrals to study child development, learning barriers, effectiveness of support programs, and more.

How do I Write a Case Study in Psychology?

Follow specified case study guidelines provided by a journal or your psychology tutor. General components of clinical case studies include: background, symptoms, assessments, diagnosis, treatment, and outcomes. Interpreting the information means the researcher decides what to include or leave out. A good case study should always clarify which information is the factual description and which is an inference or the researcher’s opinion.

1. Introduction

• Provide background on the case context and why it is of interest, presenting background information like demographics, relevant history, and presenting problem.
• Compare briefly to similar published cases if applicable. Clearly state the focus/importance of the case.

2. Case Presentation

• Describe the presenting problem in detail, including symptoms, duration,and impact on daily life.
• Include client demographics like age and gender, information about social relationships, and mental health history.
• Describe all physical, emotional, and/or sensory symptoms reported by the client.
• Use patient quotes to describe the initial complaint verbatim. Follow with full-sentence summaries of relevant history details gathered, including key components that led to a working diagnosis.
• Summarize clinical exam results, namely orthopedic/neurological tests, imaging, lab tests, etc. Note actual results rather than subjective conclusions. Provide images if clearly reproducible/anonymized.
• Clearly state the working diagnosis or clinical impression before transitioning to management.

3. Management and Outcome

• Indicate the total duration of care and number of treatments given over what timeframe. Use specific names/descriptions for any therapies/interventions applied.
• Present the results of the intervention,including any quantitative or qualitative data collected.
• For outcomes, utilize visual analog scales for pain, medication usage logs, etc., if possible. Include patient self-reports of improvement/worsening of symptoms. Note the reason for discharge/end of care.

4. Discussion

• Analyze the case, exploring contributing factors, limitations of the study, and connections to existing research.
• Analyze the effectiveness of the intervention,considering factors like participant adherence, limitations of the study, and potential alternative explanations for the results.
• Identify any questions raised in the case analysis and relate insights to established theories and current research if applicable. Avoid definitive claims about physiological explanations.
• Offer clinical implications, and suggest future research directions.

5. Additional Items

• Thank specific assistants for writing support only. No patient acknowledgments.
• References should directly support any key claims or quotes included.
• Use tables/figures/images only if substantially informative. Include permissions and legends/explanatory notes.
• Provides detailed (rich qualitative) information.
• Provides insight for further research.
• Permitting investigation of otherwise impractical (or unethical) situations.

Case studies allow a researcher to investigate a topic in far more detail than might be possible if they were trying to deal with a large number of research participants (nomothetic approach) with the aim of ‘averaging’.

Because of their in-depth, multi-sided approach, case studies often shed light on aspects of human thinking and behavior that would be unethical or impractical to study in other ways.

Research that only looks into the measurable aspects of human behavior is not likely to give us insights into the subjective dimension of experience, which is important to psychoanalytic and humanistic psychologists.

Case studies are often used in exploratory research. They can help us generate new ideas (that might be tested by other methods). They are an important way of illustrating theories and can help show how different aspects of a person’s life are related to each other.

The method is, therefore, important for psychologists who adopt a holistic point of view (i.e., humanistic psychologists ).

Limitations

• Lacking scientific rigor and providing little basis for generalization of results to the wider population.
• Researchers’ own subjective feelings may influence the case study (researcher bias).
• Difficult to replicate.
• Time-consuming and expensive.
• The volume of data, together with the time restrictions in place, impacted the depth of analysis that was possible within the available resources.

Because a case study deals with only one person/event/group, we can never be sure if the case study investigated is representative of the wider body of “similar” instances. This means the conclusions drawn from a particular case may not be transferable to other settings.

Because case studies are based on the analysis of qualitative (i.e., descriptive) data , a lot depends on the psychologist’s interpretation of the information she has acquired.

This means that there is a lot of scope for Anna O , and it could be that the subjective opinions of the psychologist intrude in the assessment of what the data means.

For example, Freud has been criticized for producing case studies in which the information was sometimes distorted to fit particular behavioral theories (e.g., Little Hans ).

This is also true of Money’s interpretation of the Bruce/Brenda case study (Diamond, 1997) when he ignored evidence that went against his theory.

Breuer, J., & Freud, S. (1895).  Studies on hysteria . Standard Edition 2: London.

Curtiss, S. (1981). Genie: The case of a modern wild child .

Diamond, M., & Sigmundson, K. (1997). Sex Reassignment at Birth: Long-term Review and Clinical Implications. Archives of Pediatrics & Adolescent Medicine , 151(3), 298-304

Freud, S. (1909a). Analysis of a phobia of a five year old boy. In The Pelican Freud Library (1977), Vol 8, Case Histories 1, pages 169-306

Freud, S. (1909b). Bemerkungen über einen Fall von Zwangsneurose (Der “Rattenmann”). Jb. psychoanal. psychopathol. Forsch ., I, p. 357-421; GW, VII, p. 379-463; Notes upon a case of obsessional neurosis, SE , 10: 151-318.

Harlow J. M. (1848). Passage of an iron rod through the head.  Boston Medical and Surgical Journal, 39 , 389–393.

Harlow, J. M. (1868).  Recovery from the Passage of an Iron Bar through the Head .  Publications of the Massachusetts Medical Society. 2  (3), 327-347.

Money, J., & Ehrhardt, A. A. (1972).  Man & Woman, Boy & Girl : The Differentiation and Dimorphism of Gender Identity from Conception to Maturity. Baltimore, Maryland: Johns Hopkins University Press.

Money, J., & Tucker, P. (1975). Sexual signatures: On being a man or a woman.

Further Information

• Case Study Approach
• Case Study Method
• Enhancing the Quality of Case Studies in Health Services Research
• “We do things together” A case study of “couplehood” in dementia
• Using mixed methods for evaluating an integrative approach to cancer care: a case study

Case Study Methods and Examples

By Janet Salmons, PhD Manager, Sage Research Methods Community

What is Case Study Methodology ?

Case studies in research are both unique and uniquely confusing. The term case study is confusing because the same term is used multiple ways. The term can refer to the methodology, that is, a system of frameworks used to design a study, or the methods used to conduct it. Or, case study can refer to a type of academic writing that typically delves into a problem, process, or situation.

Case study methodology can entail the study of one or more "cases," that could be described as instances, examples, or settings where the problem or phenomenon can be examined. The researcher is tasked with defining the parameters of the case, that is, what is included and excluded. This process is called bounding the case , or setting boundaries.

Case study can be combined with other methodologies, such as ethnography, grounded theory, or phenomenology. In such studies the research on the case uses another framework to further define the study and refine the approach.

Case study is also described as a method, given particular approaches used to collect and analyze data. Case study research is conducted by almost every social science discipline: business, education, sociology, psychology. Case study research, with its reliance on multiple sources, is also a natural choice for researchers interested in trans-, inter-, or cross-disciplinary studies.

The Encyclopedia of case study research provides an overview:

The purpose of case study research is twofold: (1) to provide descriptive information and (2) to suggest theoretical relevance. Rich description enables an in-depth or sharpened understanding of the case.

It is unique given one characteristic: case studies draw from more than one data source. Case studies are inherently multimodal or mixed methods because this they use either more than one form of data within a research paradigm, or more than one form of data from different paradigms.

A case study inquiry could include multiple types of data:

multiple forms of quantitative data sources, such as Big Data + a survey

multiple forms of qualitative data sources, such as interviews + observations + documents

multiple forms of quantitative and qualitative data sources, such as surveys + interviews

Case study methodology can be used to achieve different research purposes.

Robert Yin , methodologist most associated with case study research, differentiates between descriptive , exploratory and explanatory case studies:

Descriptive : A case study whose purpose is to describe a phenomenon. Explanatory : A case study whose purpose is to explain how or why some condition came to be, or why some sequence of events occurred or did not occur. Exploratory: A case study whose purpose is to identify the research questions or procedures to be used in a subsequent study.

Robert Yin’s book is a comprehensive guide for case study researchers!

You can read the preface and Chapter 1 of Yin's book here . See the open-access articles below for some published examples of qualitative, quantitative, and mixed methods case study research.

Mills, A. J., Durepos, G., & Wiebe, E. (2010).  Encyclopedia of case study research (Vols. 1-0). Thousand Oaks, CA: SAGE Publications, Inc. doi: 10.4135/9781412957397

Yin, R. K. (2018). Case study research and applications (6th ed.). Thousand Oaks: SAGE Publications.

Open-Access Articles Using Case Study Methodology

As you can see from this collection, case study methods are used in qualitative, quantitative and mixed methods research.

Ang, C.-S., Lee, K.-F., & Dipolog-Ubanan, G. F. (2019). Determinants of First-Year Student Identity and Satisfaction in Higher Education: A Quantitative Case Study. SAGE Open. https://doi.org/10.1177/2158244019846689

Abstract. First-year undergraduates’ expectations and experience of university and student engagement variables were investigated to determine how these perceptions influence their student identity and overall course satisfaction. Data collected from 554 first-year undergraduates at a large private university were analyzed. Participants were given the adapted version of the Melbourne Centre for the Study of Higher Education Survey to self-report their learning experience and engagement in the university community. The results showed that, in general, the students’ reasons of pursuing tertiary education were to open the door to career opportunities and skill development. Moreover, students’ views on their learning and university engagement were at the moderate level. In relation to student identity and overall student satisfaction, it is encouraging to state that their perceptions of studentship and course satisfaction were rather positive. After controlling for demographics, student engagement appeared to explain more variance in student identity, whereas students’ expectations and experience explained greater variance in students’ overall course satisfaction. Implications for practice, limitations, and recommendation of this study are addressed.

Baker, A. J. (2017). Algorithms to Assess Music Cities: Case Study—Melbourne as a Music Capital. SAGE Open. https://doi.org/10.1177/2158244017691801

Abstract. The global  Mastering of a Music City  report in 2015 notes that the concept of music cities has penetrated the global political vernacular because it delivers “significant economic, employment, cultural and social benefits.” This article highlights that no empirical study has combined all these values and offers a relevant and comprehensive definition of a music city. Drawing on industry research,1 the article assesses how mathematical flowcharts, such as Algorithm A (Economics), Algorithm B (Four T’s creative index), and Algorithm C (Heritage), have contributed to the definition of a music city. Taking Melbourne as a case study, it illustrates how Algorithms A and B are used as disputed evidence about whether the city is touted as Australia’s music capital. The article connects the three algorithms to an academic framework from musicology, urban studies, cultural economics, and sociology, and proposes a benchmark Algorithm D (Music Cities definition), which offers a more holistic assessment of music activity in any urban context. The article concludes by arguing that Algorithm D offers a much-needed definition of what comprises a music city because it builds on the popular political economy focus and includes the social importance of space and cultural practices.

Brown, K., & Mondon, A. (2020). Populism, the media, and the mainstreaming of the far right: The Guardian’s coverage of populism as a case study. Politics. https://doi.org/10.1177/0263395720955036

Abstract. Populism seems to define our current political age. The term is splashed across the headlines, brandished in political speeches and commentaries, and applied extensively in numerous academic publications and conferences. This pervasive usage, or populist hype, has serious implications for our understanding of the meaning of populism itself and for our interpretation of the phenomena to which it is applied. In particular, we argue that its common conflation with far-right politics, as well as its breadth of application to other phenomena, has contributed to the mainstreaming of the far right in three main ways: (1) agenda-setting power and deflection, (2) euphemisation and trivialisation, and (3) amplification. Through a mixed-methods approach to discourse analysis, this article uses  The Guardian  newspaper as a case study to explore the development of the populist hype and the detrimental effects of the logics that it has pushed in public discourse.

Droy, L. T., Goodwin, J., & O’Connor, H. (2020). Methodological Uncertainty and Multi-Strategy Analysis: Case Study of the Long-Term Effects of Government Sponsored Youth Training on Occupational Mobility. Bulletin of Sociological Methodology/Bulletin de Méthodologie Sociologique, 147–148(1–2), 200–230. https://doi.org/10.1177/0759106320939893

Abstract. Sociological practitioners often face considerable methodological uncertainty when undertaking a quantitative analysis. This methodological uncertainty encompasses both data construction (e.g. defining variables) and analysis (e.g. selecting and specifying a modelling procedure). Methodological uncertainty can lead to results that are fragile and arbitrary. Yet, many practitioners may be unaware of the potential scale of methodological uncertainty in quantitative analysis, and the recent emergence of techniques for addressing it. Recent proposals for ‘multi-strategy’ approaches seek to identify and manage methodological uncertainty in quantitative analysis. We present a case-study of a multi-strategy analysis, applied to the problem of estimating the long-term impact of 1980s UK government-sponsored youth training. We use this case study to further highlight the problem of cumulative methodological fragilities in applied quantitative sociology and to discuss and help develop multi-strategy analysis as a tool to address them.

Ebneyamini, S., & Sadeghi Moghadam, M. R. (2018). Toward Developing a Framework for Conducting Case Study Research .  International Journal of Qualitative Methods .  https://doi.org/10.1177/1609406918817954

Abstract. This article reviews the use of case study research for both practical and theoretical issues especially in management field with the emphasis on management of technology and innovation. Many researchers commented on the methodological issues of the case study research from their point of view thus, presenting a comprehensive framework was missing. We try representing a general framework with methodological and analytical perspective to design, develop, and conduct case study research. To test the coverage of our framework, we have analyzed articles in three major journals related to the management of technology and innovation to approve our framework. This study represents a general structure to guide, design, and fulfill a case study research with levels and steps necessary for researchers to use in their research.

Lai, D., & Roccu, R. (2019). Case study research and critical IR: the case for the extended case methodology. International Relations , 33 (1), 67-87. https://doi.org/10.1177/0047117818818243

Abstract. Discussions on case study methodology in International Relations (IR) have historically been dominated by positivist and neopositivist approaches. However, these are problematic for critical IR research, pointing to the need for a non-positivist case study methodology. To address this issue, this article introduces and adapts the extended case methodology as a critical, reflexivist approach to case study research, whereby the case is constructed through a dynamic interaction with theory, rather than selected, and knowledge is produced through extensions rather than generalisation. Insofar as it seeks to study the world in complex and non-linear terms, take context and positionality seriously, and generate explicitly political and emancipatory knowledge, the extended case methodology is consistent with the ontological and epistemological commitments of several critical IR approaches. Its potential is illustrated in the final part of the article with reference to researching the socioeconomic dimension of transitional justice in Bosnia and Herzegovina.

Lynch, R., Young, J. C., Boakye-Achampong, S., Jowaisas, C., Sam, J., & Norlander, B. (2020). Benefits of crowdsourcing for libraries: A case study from Africa . IFLA Journal. https://doi.org/10.1177/0340035220944940

Abstract. Many libraries in the Global South do not collect comprehensive data about themselves, which creates challenges in terms of local and international visibility. Crowdsourcing is an effective tool that engages the public to collect missing data, and it has proven to be particularly valuable in countries where governments collect little public data. Whereas crowdsourcing is often used within fields that have high levels of development funding, such as health, the authors believe that this approach would have many benefits for the library field as well. They present qualitative and quantitative evidence from 23 African countries involved in a crowdsourcing project to map libraries. The authors find benefits in terms of increased connections between stakeholders, capacity-building, and increased local visibility. These findings demonstrate the potential of crowdsourced approaches for tasks such as mapping to benefit libraries and similarly positioned institutions in the Global South in multifaceted ways.

Mason, W., Morris, K., Webb, C., Daniels, B., Featherstone, B., Bywaters, P., Mirza, N., Hooper, J., Brady, G., Bunting, L., & Scourfield, J. (2020). Toward Full Integration of Quantitative and Qualitative Methods in Case Study Research: Insights From Investigating Child Welfare Inequalities. Journal of Mixed Methods Research, 14 (2), 164-183. https://doi.org/10.1177/1558689819857972

Abstract. Delineation of the full integration of quantitative and qualitative methods throughout all stages of multisite mixed methods case study projects remains a gap in the methodological literature. This article offers advances to the field of mixed methods by detailing the application and integration of mixed methods throughout all stages of one such project; a study of child welfare inequalities. By offering a critical discussion of site selection and the management of confirmatory, expansionary and discordant data, this article contributes to the limited body of mixed methods exemplars specific to this field. We propose that our mixed methods approach provided distinctive insights into a complex social problem, offering expanded understandings of the relationship between poverty, child abuse, and neglect.

Rashid, Y., Rashid, A., Warraich, M. A., Sabir, S. S., & Waseem, A. (2019). Case Study Method: A Step-by-Step Guide for Business Researchers .  International Journal of Qualitative Methods .  https://doi.org/10.1177/1609406919862424

Abstract. Qualitative case study methodology enables researchers to conduct an in-depth exploration of intricate phenomena within some specific context. By keeping in mind research students, this article presents a systematic step-by-step guide to conduct a case study in the business discipline. Research students belonging to said discipline face issues in terms of clarity, selection, and operationalization of qualitative case study while doing their final dissertation. These issues often lead to confusion, wastage of valuable time, and wrong decisions that affect the overall outcome of the research. This article presents a checklist comprised of four phases, that is, foundation phase, prefield phase, field phase, and reporting phase. The objective of this article is to provide novice researchers with practical application of this checklist by linking all its four phases with the authors’ experiences and learning from recently conducted in-depth multiple case studies in the organizations of New Zealand. Rather than discussing case study in general, a targeted step-by-step plan with real-time research examples to conduct a case study is given.

VanWynsberghe, R., & Khan, S. (2007). Redefining Case Study. International Journal of Qualitative Methods, 80–94. https://doi.org/10.1177/160940690700600208

Abstract. In this paper the authors propose a more precise and encompassing definition of case study than is usually found. They support their definition by clarifying that case study is neither a method nor a methodology nor a research design as suggested by others. They use a case study prototype of their own design to propose common properties of case study and demonstrate how these properties support their definition. Next, they present several living myths about case study and refute them in relation to their definition. Finally, they discuss the interplay between the terms case study and unit of analysis to further delineate their definition of case study. The target audiences for this paper include case study researchers, research design and methods instructors, and graduate students interested in case study research.

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Case Study Method – 18 Advantages and Disadvantages

The case study method uses investigatory research as a way to collect data about specific demographics. This approach can apply to individuals, businesses, groups, or events. Each participant receives an equal amount of participation, offering information for collection that can then find new insights into specific trends, ideas, of hypotheses.

Interviews and research observation are the two standard methods of data collection used when following the case study method.

Researchers initially developed the case study method to develop and support hypotheses in clinical medicine. The benefits found in these efforts led the approach to transition to other industries, allowing for the examination of results through proposed decisions, processes, or outcomes. Its unique approach to information makes it possible for others to glean specific points of wisdom that encourage growth.

Several case study method advantages and disadvantages can appear when researchers take this approach.

List of the Advantages of the Case Study Method

1. It requires an intensive study of a specific unit. Researchers must document verifiable data from direct observations when using the case study method. This work offers information about the input processes that go into the hypothesis under consideration. A casual approach to data-gathering work is not effective if a definitive outcome is desired. Each behavior, choice, or comment is a critical component that can verify or dispute the ideas being considered.

Intensive programs can require a significant amount of work for researchers, but it can also promote an improvement in the data collected. That means a hypothesis can receive immediate verification in some situations.

2. No sampling is required when following the case study method. This research method studies social units in their entire perspective instead of pulling individual data points out to analyze them. That means there is no sampling work required when using the case study method. The hypothesis under consideration receives support because it works to turn opinions into facts, verifying or denying the proposals that outside observers can use in the future.

Although researchers might pay attention to specific incidents or outcomes based on generalized behaviors or ideas, the study itself won’t sample those situations. It takes a look at the “bigger vision” instead.

3. This method offers a continuous analysis of the facts. The case study method will look at the facts continuously for the social group being studied by researchers. That means there aren’t interruptions in the process that could limit the validity of the data being collected through this work. This advantage reduces the need to use assumptions when drawing conclusions from the information, adding validity to the outcome of the study over time. That means the outcome becomes relevant to both sides of the equation as it can prove specific suppositions or invalidate a hypothesis under consideration.

This advantage can lead to inefficiencies because of the amount of data being studied by researchers. It is up to the individuals involved in the process to sort out what is useful and meaningful and what is not.

4. It is a useful approach to take when formulating a hypothesis. Researchers will use the case study method advantages to verify a hypothesis under consideration. It is not unusual for the collected data to lead people toward the formulation of new ideas after completing this work. This process encourages further study because it allows concepts to evolve as people do in social or physical environments. That means a complete data set can be gathered based on the skills of the researcher and the honesty of the individuals involved in the study itself.

Although this approach won’t develop a societal-level evaluation of a hypothesis, it can look at how specific groups will react in various circumstances. That information can lead to a better decision-making process in the future for everyone involved.

5. It provides an increase in knowledge. The case study method provides everyone with analytical power to increase knowledge. This advantage is possible because it uses a variety of methodologies to collect information while evaluating a hypothesis. Researchers prefer to use direct observation and interviews to complete their work, but it can also advantage through the use of questionnaires. Participants might need to fill out a journal or diary about their experiences that can be used to study behaviors or choices.

Some researchers incorporate memory tests and experimental tasks to determine how social groups will interact or respond in specific situations. All of this data then works to verify the possibilities that a hypothesis proposes.

6. The case study method allows for comparisons. The human experience is one that is built on individual observations from group situations. Specific demographics might think, act, or respond in particular ways to stimuli, but each person in that group will also contribute a small part to the whole. You could say that people are sponges that collect data from one another every day to create individual outcomes.

The case study method allows researchers to take the information from each demographic for comparison purposes. This information can then lead to proposals that support a hypothesis or lead to its disruption.

7. Data generalization is possible using the case study method. The case study method provides a foundation for data generalization, allowing researches to illustrate their statistical findings in meaningful ways. It puts the information into a usable format that almost anyone can use if they have the need to evaluate the hypothesis under consideration. This process makes it easier to discover unusual features, unique outcomes, or find conclusions that wouldn’t be available without this method. It does an excellent job of identifying specific concepts that relate to the proposed ideas that researchers were verifying through their work.

Generalization does not apply to a larger population group with the case study method. What researchers can do with this information is to suggest a predictable outcome when similar groups are placed in an equal situation.

8. It offers a comprehensive approach to research. Nothing gets ignored when using the case study method to collect information. Every person, place, or thing involved in the research receives the complete attention of those seeking data. The interactions are equal, which means the data is comprehensive and directly reflective of the group being observed.

This advantage means that there are fewer outliers to worry about when researching an idea, leading to a higher level of accuracy in the conclusions drawn by the researchers.

9. The identification of deviant cases is possible with this method. The case study method of research makes it easier to identify deviant cases that occur in each social group. These incidents are units (people) that behave in ways that go against the hypothesis under consideration. Instead of ignoring them like other options do when collecting data, this approach incorporates the “rogue” behavior to understand why it exists in the first place.

This advantage makes the eventual data and conclusions gathered more reliable because it incorporates the “alternative opinion” that exists. One might say that the case study method places as much emphasis on the yin as it does the yang so that the whole picture becomes available to the outside observer.

10. Questionnaire development is possible with the case study method. Interviews and direct observation are the preferred methods of implementing the case study method because it is cheap and done remotely. The information gathered by researchers can also lead to farming questionnaires that can farm additional data from those being studied. When all of the data resources come together, it is easier to formulate a conclusion that accurately reflects the demographics.

Some people in the case study method may try to manipulate the results for personal reasons, but this advantage makes it possible to identify this information readily. Then researchers can look into the thinking that goes into the dishonest behaviors observed.

List of the Disadvantages of the Case Study Method

1. The case study method offers limited representation. The usefulness of the case study method is limited to a specific group of representatives. Researchers are looking at a specific demographic when using this option. That means it is impossible to create any generalization that applies to the rest of society, an organization, or a larger community with this work. The findings can only apply to other groups caught in similar circumstances with the same experiences.

It is useful to use the case study method when attempting to discover the specific reasons why some people behave in a specific way. If researchers need something more generalized, then a different method must be used.

2. No classification is possible with the case study method. This disadvantage is also due to the sample size in the case study method. No classification is possible because researchers are studying such a small unit, group, or demographic. It can be an inefficient process since the skills of the researcher help to determine the quality of the data being collected to verify the validity of a hypothesis. Some participants may be unwilling to answer or participate, while others might try to guess at the outcome to support it.

Researchers can get trapped in a place where they explore more tangents than the actual hypothesis with this option. Classification can occur within the units being studied, but this data cannot extrapolate to other demographics.

3. The case study method still offers the possibility of errors. Each person has an unconscious bias that influences their behaviors and choices. The case study method can find outliers that oppose a hypothesis fairly easily thanks to its emphasis on finding facts, but it is up to the researchers to determine what information qualifies for this designation. If the results from the case study method are surprising or go against the opinion of participating individuals, then there is still the possibility that the information will not be 100% accurate.

Researchers must have controls in place that dictate how data gathering work occurs. Without this limitation in place, the results of the study cannot be guaranteed because of the presence of bias.

4. It is a subjective method to use for research. Although the purpose of the case study method of research is to gather facts, the foundation of what gets gathered is still based on opinion. It uses the subjective method instead of the objective one when evaluating data, which means there can be another layer of errors in the information to consider.

Imagine that a researcher interprets someone’s response as “angry” when performing direct observation, but the individual was feeling “shame” because of a decision they made. The difference between those two emotions is profound, and it could lead to information disruptions that could be problematic to the eventual work of hypothesis verification.

5. The processes required by the case study method are not useful for everyone. The case study method uses a person’s memories, explanations, and records from photographs and diaries to identify interactions on influences on psychological processes. People are given the chance to describe what happens in the world around them as a way for researchers to gather data. This process can be an advantage in some industries, but it can also be a worthless approach to some groups.

If the social group under study doesn’t have the information, knowledge, or wisdom to provide meaningful data, then the processes are no longer useful. Researchers must weigh the advantages and disadvantages of the case study method before starting their work to determine if the possibility of value exists. If it does not, then a different method may be necessary.

6. It is possible for bias to form in the data. It’s not just an unconscious bias that can form in the data when using the case study method. The narrow study approach can lead to outright discrimination in the data. Researchers can decide to ignore outliers or any other information that doesn’t support their hypothesis when using this method. The subjective nature of this approach makes it difficult to challenge the conclusions that get drawn from this work, and the limited pool of units (people) means that duplication is almost impossible.

That means unethical people can manipulate the results gathered by the case study method to their own advantage without much accountability in the process.

7. This method has no fixed limits to it. This method of research is highly dependent on situational circumstances rather than overarching societal or corporate truths. That means the researcher has no fixed limits of investigation. Even when controls are in place to limit bias or recommend specific activities, the case study method has enough flexibility built into its structures to allow for additional exploration. That means it is possible for this work to continue indefinitely, gathering data that never becomes useful.

Scientists began to track the health of 268 sophomores at Harvard in 1938. The Great Depression was in its final years at that point, so the study hoped to reveal clues that lead to happy and healthy lives. It continues still today, now incorporating the children of the original participants, providing over 80 years of information to sort through for conclusions.

8. The case study method is time-consuming and expensive. The case study method can be affordable in some situations, but the lack of fixed limits and the ability to pursue tangents can make it a costly process in most situations. It takes time to gather the data in the first place, and then researchers must interpret the information received so that they can use it for hypothesis evaluation. There are other methods of data collection that can be less expensive and provide results faster.

That doesn’t mean the case study method is useless. The individualization of results can help the decision-making process advance in a variety of industries successfully. It just takes more time to reach the appropriate conclusion, and that might be a resource that isn’t available.

The advantages and disadvantages of the case study method suggest that the helpfulness of this research option depends on the specific hypothesis under consideration. When researchers have the correct skills and mindset to gather data accurately, then it can lead to supportive data that can verify ideas with tremendous accuracy.

This research method can also be used unethically to produce specific results that can be difficult to challenge.

When bias enters into the structure of the case study method, the processes become inefficient, inaccurate, and harmful to the hypothesis. That’s why great care must be taken when designing a study with this approach. It might be a labor-intensive way to develop conclusions, but the outcomes are often worth the investments needed.

Strengths and Weaknesses of Case Studies

There is no doubt that case studies are a valuable and important form of research for all of the industries and fields that use them. However, along with all their advantages, they also have some disadvantages. In this article we are going to look at both.

Advantages of Case Studies

Intensive Study

Case study method is responsible for intensive study of a unit. It is the investigation and exploration of an event thoroughly and deeply. You get a very detailed and in-depth study of a person or event. This is especially the case with subjects that cannot be physically or ethically recreated.

This is one of the biggest advantages of the Genie case. You cannot lock up a child for 13 years and deprive them of everything. That would be morally and ethically wrong in every single way. So when the opportunity presented itself, researchers could not look away. It was a once in a lifetime opportunity to learn about feral children.

Genie was a feral child. She was raised in completed isolation, with little human contact. Because of the abuse she withstood, she was unable to develop cognitively. From infancy she was strapped to a potty chair, and therefore never acquired the physicality needed for walking, running and jumping.

If Genie made a noise, her father beat her. Therefore, she learned to not make a noise. Once she was found, researchers studied her language skills, and attempted to find ways to get her to communicate. They were successful. While she never gained the ability to speak, she did develop other ways to communicate. However, the public soon lost interest in her case, and with that, the funds to conduct the study.

However, her case was extremely important to child development psychology and linguistic theory. Because of her, we know that mental stimulation is needed for proper development. We also now know that there is a "critical period" for the learning of language.

Developing New Research

Case studies are one of the best ways to stimulate new research. A case study can be completed, and if the findings are valuable, they can lead to new and advanced research in the field. There has been a great deal of research done that wouldn't have been possible without case studies.

An example of this is the sociological study Nickel and Dimed. Nickel and Dimed is a book and study done by Barbara Ehrenreich. She wanted to study poverty in America, and did so by living and working as a person living on minimum wage.

Through her experiment, she discovered that poverty was almost inescapable. As soon as she saved a little money, she was hit with a crisis. She might get sick, or her car might break down, all occurrences that can be destructive when a person doesn't have a safety net to fall back on.

It didn't matter where she lived or what she did. Working a minimum wage job gave her no chances for advancement or improvement whatsoever. And she did the experiment as a woman with no children to support.

This study opened a lot of eyes to the problem of the working poor in America. By living and working as the experiment, Ehrenreich was able to show first-hand data regarding the issues surrounding poverty. The book didn't end with any solutions, just suggestions for the reader and points for them to think about.

Using this case study information, new studies could be organized to learn better ways to help people who are fighting poverty, or better ways to help the working poor.

Contradicting Established Ideas or Theories

Oftentimes there are theories that may be questioned with case studies. For example, in the John/John case study, it was believed that gender and sexual identity were a construct of nurture, not nature.

John-John focused on a set of twin boys, both of whom were circumcised at the age of 6 months. One of the twin's circumcisions failed, causing irreparable damage to the penis. His parents were concerned about the sexual health of their son, so they contacted Dr. John Money for a solution.

Dr. Money believed that sexuality came from nurture, not nature, and that the injured baby, Bruce, could be raised as a girl. His penis was removed and he was sexually reassigned to become a girl. Bruce's name was changed to Brenda, and his parents decided to raise him as a girl.

In this case, Dr. Money was dishonest. He believed that gender could be changed, which has since been proven false. Brenda's parents were also dishonest, stating that the surgery was a success, when in fact that wasn't the case.

As Brenda grew up, she always acted masculine and was teased for it at school. She did not socialize as a girl, and did not identify as a female. When Brenda was 13 she learned the truth, and was incredibly relieved. She changed her name to David, and lived the rest of her life as a male.

This case proved that the general theory was wrong, and is still valuable, even though the study author was dishonest.

Giving New Insight

Case studies have the ability to give insight into phenomena that cannot be learned in any other way. An example of this is the case study about Sidney Bradford. Bradford was blind from the age of 10 months old, and regained his sight at the age of 52 from a corneal transplant.

This unique situation allowed researchers to better learn how perception and motion changes when suddenly given sight. They were able to better understand how colors and dimensions affect the human process. For what it is worth, Bradford continued to live and work with his eyes closed, as he found sight too stimulating.

Another famous study was the sociological study of Milgram.

Stanley Milgram did a study from 1960 to 1974 in which he studied the effects of social pressure. The study was set up as an independent laboratory. A random person would walk in, and agree to be a part of the study. He was told to act as a teacher, and ask questions to another volunteer, who was the learner.

The teacher would ask the learner questions, and whenever he answered incorrectly, the teacher was instructed to give the learner an electric shock. Each time the learner was wrong, the shock would be increased by 15 volts. What the teacher didn't know was that the learner was a part of the experiment, and that no shocks were being given. However, the learner did act as if they were being shocked.

If the teachers tried to quit, they were strongly pushed to continue. The goal of the experiment was to see whether or not any of the teachers would go up to the highest voltage. As it turned out, 65% of the teachers did.

This study opened eyes when it comes to social pressure. If someone tells you it is okay to hurt someone, at what point will the person back off and say "this is not ok!" And in this study, the results were the same, regardless of income, race, gender or ethnicity.

This study opened up the sociological world of understanding the divide between social pressure and morality.

Disadvantages of Case Studies

Inability to Replicate

As demonstrated with the Genie case study, many studies cannot be replicated, and therefore, cannot be corroborated. Because the studies cannot be replicated, it means the data and results are only valid for that one person. Now, one could infer that that results of the Genie study would be the same with other feral children, without additional studies we can never be 100% certain.

Also, Genie was a white, American female. We do not know whether someone with a different gender, race or ethnicity would have a different result.

Key Term! Hawthorne Effect

The effect in which people change their behavior when they are aware they are being observed.

Researcher Bias

When conducting a case study, it is very possible for the author to form a bias. This bias can be for the subject; the form of data collection, or the way the data is interpreted. This is very common, since it is normal for humans to be subjective. It is well known that Sigmund Freud, the father of psychology, was often biased in his case histories and interpretations.

The researcher can become close to a study participant, or may learn to identify with the subject. When this happens the researcher loses their perspective as an outsider.

No Classification

Any classification is not possible due to studying a small unit. This generalization of results is limited, since the study is only focusing on one small group. However, this isn't always a problem, especially if generalization is not one of the study's goals.

Time Intensive

Case studies can be very time consuming. The data collection process can be very intensive and long, and this is something new researchers are not familiar with. It takes a long period of time to develop a case study, and develop a detailed analysis.

Many studies also require the authors to immerse themselves in the case. For example, in the Genie case, the lead researchers spent an abnormal amount of time with Genie, since so few people knew how to handle her. David Rigler, one of the lead researchers, actually had Genie live with him and his family for years. Because of this attachment, many questioned the veracity of the study data.

Possibility of Errors

Case study method may have errors of memory or judgment. Since reconstructing case history is based on memory, this can lead to errors. Also, how one person perceived the past could be different for another person, and this can and does lead to errors.

When considering various aspects of their lives, people tend to focus on issues that they find most important. This allows them to form a prejudice and can make them unaware of other possible options.

Ethical Issues

With small studies, there is always the question of ethics. At what point does a study become unethical? The Genie case was riddled with accusations of being unethical, and people still debate about it today.

Was it ethical to study Genie as deeply as she was studied?

Did Genie deserve to live out her life unbothered by researchers and academics trying to use her case to potentially further their careers?

At what point does the pursuit of scientific knowledge outweigh the right to a life free from research?

Also, because the researchers became so invested in the study, people questioned whether a researcher would report unethical behavior if they witnessed it.

Advantages and Disadvantages in Real-Life Studies

Two of these case studies are the Tylenol Scandal and the Genie language study.

Let's look at the advantages and disadvantages of these two studies.

Genie – Advantages

Uniqueness of study – Being able to study a feral child is a rare occurrence.

Genie – Disadvantages

Ethics - The lead researcher David Rigler provided a home for Genie, and was paid for being a foster parent. This is often seen as unethical, since Rigler had a financial interest in Genie and her case.

Tylenol – Advantages

Uniqueness of study – What happened to Tylenol was very unique and rare. While companies face crisis all the time, a public health crisis of this magnitude is very unique.

Tylenol – Disadvantages

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The Case Study as Research Method: A Practical Handbook

Qualitative Research in Accounting & Management

ISSN : 1176-6093

Article publication date: 21 June 2011

Scapens, R.W. (2011), "The Case Study as Research Method: A Practical Handbook", Qualitative Research in Accounting & Management , Vol. 8 No. 2, pp. 201-204. https://doi.org/10.1108/11766091111137582

Emerald Group Publishing Limited

Copyright © 2011, Emerald Group Publishing Limited

This book aims to provide case‐study researchers with a step‐by‐step practical guide to “help them conduct the study with the required degree of rigour” (p. xi).

It seeks to “demonstrate that the case study is indeed a scientific method” (p. 104) and to show “the usefulness of the case method as one tool in the researcher's methodological arsenal” (p. 105). The individual chapters cover the various stages in conducting case‐study research, and each chapter sets out a number of practical steps which have to be taken by the researcher. The following are the eight stages/chapters and, in brackets, the number of steps in each stages:

Assessing appropriateness and usefulness (4).

Ensuring accuracy of results (21).

Preparation (6).

Selecting cases (4).

Collecting data (7).

Analyzing data (4).

Interpreting data (3).

Reporting results (4).

It is particularly noticeable that ensuring accuracy of results has by far the largest number of number of steps – 21 steps compared to seven or fewer steps in the other stages. This reflects Gagnon's concern to demonstrate the scientific rigour of case‐study research. In the forward, he explains that the book draws on his experience in conducting his own PhD research, which was closely supervised by three professors, one of whom was inclined towards quantitative research. Consequently, his research was underpinned by the principles and philosophy of quantitative research. This is clearly reflected in the approach taken in this book, which seeks to show that case‐study research is just as rigorous and scientific as quantitative research, and it can produce an objective and accurate representation of the observed reality.

There is no discussion of the methodological issues relating to the use of case‐study research methods. This is acknowledged in the forward, although Gagnon refers to them as philosophical or epistemological issues (p. xii), as he tends to use the terms methodology and method interchangeably – as is common in quantitative research. Although he starts (step 1.1) by trying to distance case and other qualitative research from the work of positivists, arguing that society is socially constructed, he nevertheless sees social reality as objective and independent of the researcher. So for Gagnon, the aim of case research is to accurately reflect that reality. At various points in the book the notion of interpretation is used – evidence is interpreted and the (objective) case findings have to be interpreted.

So although there is a distancing from positivist research (p. 1), the approach taken in this book retains an objective view of the social reality which is being researched; a view which is rather different to the subjective view of reality taken by many interpretive case researchers. This distinction between an objective and a subjective view of the social reality being researched – and especially its use in contrasting positivist and interpretive research – has its origins the taxonomy of Burrell and Morgan (1979) . Although there have been various developments in the so‐called “objective‐subjective debate”, and recently some discussion in relation to management accounting research ( Kakkuri‐Knuuttila et al. , 2008 ; Ahrens, 2008 ), this debate is not mentioned in the book. Nevertheless, it is clear that Gagnon is firmly in the objective camp. In a recent paper, Johnson et al. (2006, p. 138) provide a more contemporary classification of the different types of qualitative research. In their terms, the approach taken in this book could be described as neo‐empiricist – an approach which they characterise as “qualitative positivists”.

The approach taken in this handbook leaves case studies open to the criticisms that they are a small sample, and consequently difficult to generalise, and to arguments that case studies are most appropriate for exploratory research which can subsequently be generalised though quantitative research. Gagnon explains that this was the approach he used after completing his thesis (p. xi). The handbook only seems to recognise two types of case studies, namely exploratory and raw empirical case studies – the latter being used where “the researcher is interested in a subject without having formed any preconceived ideas about it” (p. 15) – which has echoes of Glaser and Strauss (1967) . However, limiting case studies to these two types ignores other potential types; in particular, explanatory case studies which are where interpretive case‐study research can make important contributions ( Ryan et al. , 2002 ).

This limited approach to case studies comes through in the practical steps which are recommended in the handbook, and especially in the discussion of reliability and validity. The suggested steps seem to be designed to keep very close to the notions of reliability and validity used in quantitative research. There is no mention of the recent discussion of “validity” in interpretive accounting research, which emphasises the importance of authenticity and credibility and their implications for writing up qualitative and case‐study research ( Lukka and Modell, 2010 ). Although the final stage of Gagnon's handbook makes some very general comments about reporting the results, it does not mention, for example, Baxter and Chua's (2008) paper in QRAM which discusses the importance of demonstrating authenticity, credibility and transferability in writing qualitative research.

Despite Gagnon's emphasis on traditional notions of reliability and validity the handbook provides some useful practical advice for all case‐study researchers. For example, case‐study research needs a very good research design; case‐study researchers must work hard to gain access to and acceptance in the research settings; a clear strategy is needed for data collection; the case researcher should create field notes (in a field notebook, or otherwise) to record all the thoughts, ideas, observations, etc. that would not otherwise be collected; and the vast amount of data that case‐study research can generate needs to be carefully managed. Furthermore, because of what Gagnon calls the “risk of mortality” (p. 54) (i.e. the risk that access to a research site may be lost – for instance, if the organisation goes bankrupt) it is crucial for some additional site(s) to be selected at the outset to ensure that the planned research can be completed. This is what I call “insurance cases” when talking to my own PhD students. Interestingly, Gagnon recognises the ethical issues involved in doing case studies – something which is not always mentioned by the more objectivist type of case‐study researchers. He emphasises that it is crucial to honour confidentiality agreements, to ensure data are stored securely and that commitments are met and promises kept.

There is an interesting discussion of the advantages and disadvantages of using computer methods in analysing data (in stage 6). However, the discussion of coding appears to be heavily influenced by grounded theory, and is clearly concerned with producing an accurate reflection of an objective reality. In addition, Gagnon's depiction of case analysis is overly focussed on content analysis – possibly because it is a quantitative type of technique. There is no reference to the other approaches available to qualitative researchers. For example, there is no mention of the various visualisation techniques set out in Miles and Huberman (1994) .

To summarise, Gagnon's book is particularly useful for case‐study researchers who see the reality they are researching as objective and researcher independent. However, this is a sub‐set of case‐study researchers. Although some of the practical guidance offered is relevant for other types of case‐study researchers, those who see multiple realities in the social actors and/or recognise the subjectivity of the research process might have difficulty with some of the steps in this handbook. Gagnon's aim to show that the case study is a scientific method, gives the handbook a focus on traditional (quantitatively inspired) notions rigour and validity, and a tendency to ignore (or at least marginalise) other types of case study research. For example, the focus on exploratory cases, which need to be supplemented by broad based quantitative research, overlooks the real potential of case study research which lies in explanatory cases. Furthermore, Gagnon is rather worried about participant research, as the researcher may play a role which is “not consistent with scientific method” (p. 42), and which may introduce researcher bias and thereby damage “the impartiality of the study” (p. 53). Leaving aside the philosophical question about whether any social science research, including quantitative research, can be impartial, this stance could severely limit the potential of case‐study research and it would rule out both the early work on the sociology of mass production and the recent calls for interventionist research. Clearly, there could be a problem where a researcher is trying to sell consulting services, but there is a long tradition of social researchers working within organisations that they are studying. Furthermore, if interpretive research is to be relevant for practice, researchers may have to work with organisations to introduce new ideas and new ways of analysing problems. Gagnon would seem to want to avoid all such research – as it would not be “impartial”.

Consequently, although there is some good practical advice for case study researchers in this handbook, some of the recommendations have to be treated cautiously, as it is a book which sees case‐study research in a very specific way. As mentioned earlier, in the Forward Gagnon explicitly recognises that the book does not take a position on the methodological debates surrounding the use of case studies as a research method, and he says that “The reader should therefore use and judge this handbook with these considerations in mind” (p. xii). This is very good advice – caveat emptor .

Ahrens , T. ( 2008 ), “ A comment on Marja‐Liisa Kakkuri‐Knuuttila ”, Accounting, Organizations and Society , Vol. 33 Nos 2/3 , pp. 291 ‐ 7 , Kari Lukka and Jaakko Kuorikoski.

Baxter , J. and Chua , W.F. ( 2008 ), “ The field researcher as author‐writer ”, Qualitative Research in Accounting & Management , Vol. 5 No. 2 , pp. 101 ‐ 21 .

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Kakkuri‐Knuuttila , M.‐L. , Lukka , K. and Kuorikoski , J. ( 2008 ), “ Straddling between paradigms: a naturalistic philosophical case study on interpretive research in management accounting ”, Accounting, Organizations and Society , Vol. 33 Nos 2/3 , pp. 267 ‐ 91 .

Lukka , K. and Modell , S. ( 2010 ), “ Validation in interpretive management accounting research ”, Accounting, Organizations and Society , Vol. 35 , pp. 462 ‐ 77 .

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5 Benefits of Learning Through the Case Study Method

• 28 Nov 2023

While several factors make HBS Online unique —including a global Community and real-world outcomes —active learning through the case study method rises to the top.

In a 2023 City Square Associates survey, 74 percent of HBS Online learners who also took a course from another provider said HBS Online’s case method and real-world examples were better by comparison.

Here’s a primer on the case method, five benefits you could gain, and how to experience it for yourself.

Access your free e-book today.

What Is the Harvard Business School Case Study Method?

The case study method , or case method , is a learning technique in which you’re presented with a real-world business challenge and asked how you’d solve it. After working through it yourself and with peers, you’re told how the scenario played out.

HBS pioneered the case method in 1922. Shortly before, in 1921, the first case was written.

“How do you go into an ambiguous situation and get to the bottom of it?” says HBS Professor Jan Rivkin, former senior associate dean and chair of HBS's master of business administration (MBA) program, in a video about the case method . “That skill—the skill of figuring out a course of inquiry to choose a course of action—that skill is as relevant today as it was in 1921.”

Originally developed for the in-person MBA classroom, HBS Online adapted the case method into an engaging, interactive online learning experience in 2014.

In HBS Online courses , you learn about each case from the business professional who experienced it. After reviewing their videos, you’re prompted to take their perspective and explain how you’d handle their situation.

You then get to read peers’ responses, “star” them, and comment to further the discussion. Afterward, you learn how the professional handled it and their key takeaways.

HBS Online’s adaptation of the case method incorporates the famed HBS “cold call,” in which you’re called on at random to make a decision without time to prepare.

“Learning came to life!” said Sheneka Balogun , chief administration officer and chief of staff at LeMoyne-Owen College, of her experience taking the Credential of Readiness (CORe) program . “The videos from the professors, the interactive cold calls where you were randomly selected to participate, and the case studies that enhanced and often captured the essence of objectives and learning goals were all embedded in each module. This made learning fun, engaging, and student-friendly.”

If you’re considering taking a course that leverages the case study method, here are five benefits you could experience.

5 Benefits of Learning Through Case Studies

1. take new perspectives.

The case method prompts you to consider a scenario from another person’s perspective. To work through the situation and come up with a solution, you must consider their circumstances, limitations, risk tolerance, stakeholders, resources, and potential consequences to assess how to respond.

Taking on new perspectives not only can help you navigate your own challenges but also others’. Putting yourself in someone else’s situation to understand their motivations and needs can go a long way when collaborating with stakeholders.

2. Hone Your Decision-Making Skills

Another skill you can build is the ability to make decisions effectively . The case study method forces you to use limited information to decide how to handle a problem—just like in the real world.

Throughout your career, you’ll need to make difficult decisions with incomplete or imperfect information—and sometimes, you won’t feel qualified to do so. Learning through the case method allows you to practice this skill in a low-stakes environment. When facing a real challenge, you’ll be better prepared to think quickly, collaborate with others, and present and defend your solution.

3. Become More Open-Minded

As you collaborate with peers on responses, it becomes clear that not everyone solves problems the same way. Exposing yourself to various approaches and perspectives can help you become a more open-minded professional.

When you’re part of a diverse group of learners from around the world, your experiences, cultures, and backgrounds contribute to a range of opinions on each case.

On the HBS Online course platform, you’re prompted to view and comment on others’ responses, and discussion is encouraged. This practice of considering others’ perspectives can make you more receptive in your career.

“You’d be surprised at how much you can learn from your peers,” said Ratnaditya Jonnalagadda , a software engineer who took CORe.

In addition to interacting with peers in the course platform, Jonnalagadda was part of the HBS Online Community , where he networked with other professionals and continued discussions sparked by course content.

“You get to understand your peers better, and students share examples of businesses implementing a concept from a module you just learned,” Jonnalagadda said. “It’s a very good way to cement the concepts in one's mind.”

4. Enhance Your Curiosity

One byproduct of taking on different perspectives is that it enables you to picture yourself in various roles, industries, and business functions.

“Each case offers an opportunity for students to see what resonates with them, what excites them, what bores them, which role they could imagine inhabiting in their careers,” says former HBS Dean Nitin Nohria in the Harvard Business Review . “Cases stimulate curiosity about the range of opportunities in the world and the many ways that students can make a difference as leaders.”

Through the case method, you can “try on” roles you may not have considered and feel more prepared to change or advance your career .

5. Build Your Self-Confidence

Finally, learning through the case study method can build your confidence. Each time you assume a business leader’s perspective, aim to solve a new challenge, and express and defend your opinions and decisions to peers, you prepare to do the same in your career.

According to a 2022 City Square Associates survey , 84 percent of HBS Online learners report feeling more confident making business decisions after taking a course.

“Self-confidence is difficult to teach or coach, but the case study method seems to instill it in people,” Nohria says in the Harvard Business Review . “There may well be other ways of learning these meta-skills, such as the repeated experience gained through practice or guidance from a gifted coach. However, under the direction of a masterful teacher, the case method can engage students and help them develop powerful meta-skills like no other form of teaching.”

How to Experience the Case Study Method

If the case method seems like a good fit for your learning style, experience it for yourself by taking an HBS Online course. Offerings span seven subject areas, including:

• Business essentials
• Leadership and management
• Entrepreneurship and innovation
• Finance and accounting
• Business in society

No matter which course or credential program you choose, you’ll examine case studies from real business professionals, work through their challenges alongside peers, and gain valuable insights to apply to your career.

Are you interested in discovering how HBS Online can help advance your career? Explore our course catalog and download our free guide —complete with interactive workbook sections—to determine if online learning is right for you and which course to take.

About the Author

• First Online: 27 October 2022

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• Rajendra Baikady 5  

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This chapter reviews the strengths and limitations of case study as a research method in social sciences. It provides an account of an evidence base to justify why a case study is best suitable for some research questions and why not for some other research questions. Case study designing around the research context, defining the structure and modality, conducting the study, collecting the data through triangulation mode, analysing the data, and interpreting the data and theory building at the end give a holistic view of it. In addition, the chapter also focuses on the types of case study and when and where to use case study as a research method in social science research.

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Channaveer, R.M., Baikady, R. (2022). Case Study. In: Islam, M.R., Khan, N.A., Baikady, R. (eds) Principles of Social Research Methodology. Springer, Singapore. https://doi.org/10.1007/978-981-19-5441-2_21

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Methodology or method? A critical review of qualitative case study reports

Despite on-going debate about credibility, and reported limitations in comparison to other approaches, case study is an increasingly popular approach among qualitative researchers. We critically analysed the methodological descriptions of published case studies. Three high-impact qualitative methods journals were searched to locate case studies published in the past 5 years; 34 were selected for analysis. Articles were categorized as health and health services ( n= 12), social sciences and anthropology ( n= 7), or methods ( n= 15) case studies. The articles were reviewed using an adapted version of established criteria to determine whether adequate methodological justification was present, and if study aims, methods, and reported findings were consistent with a qualitative case study approach. Findings were grouped into five themes outlining key methodological issues: case study methodology or method, case of something particular and case selection, contextually bound case study, researcher and case interactions and triangulation, and study design inconsistent with methodology reported. Improved reporting of case studies by qualitative researchers will advance the methodology for the benefit of researchers and practitioners.

Case study research is an increasingly popular approach among qualitative researchers (Thomas, 2011 ). Several prominent authors have contributed to methodological developments, which has increased the popularity of case study approaches across disciplines (Creswell, 2013b ; Denzin & Lincoln, 2011b ; Merriam, 2009 ; Ragin & Becker, 1992 ; Stake, 1995 ; Yin, 2009 ). Current qualitative case study approaches are shaped by paradigm, study design, and selection of methods, and, as a result, case studies in the published literature vary. Differences between published case studies can make it difficult for researchers to define and understand case study as a methodology.

Experienced qualitative researchers have identified case study research as a stand-alone qualitative approach (Denzin & Lincoln, 2011b ). Case study research has a level of flexibility that is not readily offered by other qualitative approaches such as grounded theory or phenomenology. Case studies are designed to suit the case and research question and published case studies demonstrate wide diversity in study design. There are two popular case study approaches in qualitative research. The first, proposed by Stake ( 1995 ) and Merriam ( 2009 ), is situated in a social constructivist paradigm, whereas the second, by Yin ( 2012 ), Flyvbjerg ( 2011 ), and Eisenhardt ( 1989 ), approaches case study from a post-positivist viewpoint. Scholarship from both schools of inquiry has contributed to the popularity of case study and development of theoretical frameworks and principles that characterize the methodology.

The diversity of case studies reported in the published literature, and on-going debates about credibility and the use of case study in qualitative research practice, suggests that differences in perspectives on case study methodology may prevent researchers from developing a mutual understanding of practice and rigour. In addition, discussion about case study limitations has led some authors to query whether case study is indeed a methodology (Luck, Jackson, & Usher, 2006 ; Meyer, 2001 ; Thomas, 2010 ; Tight, 2010 ). Methodological discussion of qualitative case study research is timely, and a review is required to analyse and understand how this methodology is applied in the qualitative research literature. The aims of this study were to review methodological descriptions of published qualitative case studies, to review how the case study methodological approach was applied, and to identify issues that need to be addressed by researchers, editors, and reviewers. An outline of the current definitions of case study and an overview of the issues proposed in the qualitative methodological literature are provided to set the scene for the review.

Definitions of qualitative case study research

Case study research is an investigation and analysis of a single or collective case, intended to capture the complexity of the object of study (Stake, 1995 ). Qualitative case study research, as described by Stake ( 1995 ), draws together “naturalistic, holistic, ethnographic, phenomenological, and biographic research methods” in a bricoleur design, or in his words, “a palette of methods” (Stake, 1995 , pp. xi–xii). Case study methodology maintains deep connections to core values and intentions and is “particularistic, descriptive and heuristic” (Merriam, 2009 , p. 46).

As a study design, case study is defined by interest in individual cases rather than the methods of inquiry used. The selection of methods is informed by researcher and case intuition and makes use of naturally occurring sources of knowledge, such as people or observations of interactions that occur in the physical space (Stake, 1998 ). Thomas ( 2011 ) suggested that “analytical eclecticism” is a defining factor (p. 512). Multiple data collection and analysis methods are adopted to further develop and understand the case, shaped by context and emergent data (Stake, 1995 ). This qualitative approach “explores a real-life, contemporary bounded system (a case ) or multiple bounded systems (cases) over time, through detailed, in-depth data collection involving multiple sources of information … and reports a case description and case themes ” (Creswell, 2013b , p. 97). Case study research has been defined by the unit of analysis, the process of study, and the outcome or end product, all essentially the case (Merriam, 2009 ).

The case is an object to be studied for an identified reason that is peculiar or particular. Classification of the case and case selection procedures informs development of the study design and clarifies the research question. Stake ( 1995 ) proposed three types of cases and study design frameworks. These include the intrinsic case, the instrumental case, and the collective instrumental case. The intrinsic case is used to understand the particulars of a single case, rather than what it represents. An instrumental case study provides insight on an issue or is used to refine theory. The case is selected to advance understanding of the object of interest. A collective refers to an instrumental case which is studied as multiple, nested cases, observed in unison, parallel, or sequential order. More than one case can be simultaneously studied; however, each case study is a concentrated, single inquiry, studied holistically in its own entirety (Stake, 1995 , 1998 ).

Researchers who use case study are urged to seek out what is common and what is particular about the case. This involves careful and in-depth consideration of the nature of the case, historical background, physical setting, and other institutional and political contextual factors (Stake, 1998 ). An interpretive or social constructivist approach to qualitative case study research supports a transactional method of inquiry, where the researcher has a personal interaction with the case. The case is developed in a relationship between the researcher and informants, and presented to engage the reader, inviting them to join in this interaction and in case discovery (Stake, 1995 ). A postpositivist approach to case study involves developing a clear case study protocol with careful consideration of validity and potential bias, which might involve an exploratory or pilot phase, and ensures that all elements of the case are measured and adequately described (Yin, 2009 , 2012 ).

Current methodological issues in qualitative case study research

The future of qualitative research will be influenced and constructed by the way research is conducted, and by what is reviewed and published in academic journals (Morse, 2011 ). If case study research is to further develop as a principal qualitative methodological approach, and make a valued contribution to the field of qualitative inquiry, issues related to methodological credibility must be considered. Researchers are required to demonstrate rigour through adequate descriptions of methodological foundations. Case studies published without sufficient detail for the reader to understand the study design, and without rationale for key methodological decisions, may lead to research being interpreted as lacking in quality or credibility (Hallberg, 2013 ; Morse, 2011 ).

There is a level of artistic license that is embraced by qualitative researchers and distinguishes practice, which nurtures creativity, innovation, and reflexivity (Denzin & Lincoln, 2011b ; Morse, 2009 ). Qualitative research is “inherently multimethod” (Denzin & Lincoln, 2011a , p. 5); however, with this creative freedom, it is important for researchers to provide adequate description for methodological justification (Meyer, 2001 ). This includes paradigm and theoretical perspectives that have influenced study design. Without adequate description, study design might not be understood by the reader, and can appear to be dishonest or inaccurate. Reviewers and readers might be confused by the inconsistent or inappropriate terms used to describe case study research approach and methods, and be distracted from important study findings (Sandelowski, 2000 ). This issue extends beyond case study research, and others have noted inconsistencies in reporting of methodology and method by qualitative researchers. Sandelowski ( 2000 , 2010 ) argued for accurate identification of qualitative description as a research approach. She recommended that the selected methodology should be harmonious with the study design, and be reflected in methods and analysis techniques. Similarly, Webb and Kevern ( 2000 ) uncovered inconsistencies in qualitative nursing research with focus group methods, recommending that methodological procedures must cite seminal authors and be applied with respect to the selected theoretical framework. Incorrect labelling using case study might stem from the flexibility in case study design and non-directional character relative to other approaches (Rosenberg & Yates, 2007 ). Methodological integrity is required in design of qualitative studies, including case study, to ensure study rigour and to enhance credibility of the field (Morse, 2011 ).

Case study has been unnecessarily devalued by comparisons with statistical methods (Eisenhardt, 1989 ; Flyvbjerg, 2006 , 2011 ; Jensen & Rodgers, 2001 ; Piekkari, Welch, & Paavilainen, 2009 ; Tight, 2010 ; Yin, 1999 ). It is reputed to be the “the weak sibling” in comparison to other, more rigorous, approaches (Yin, 2009 , p. xiii). Case study is not an inherently comparative approach to research. The objective is not statistical research, and the aim is not to produce outcomes that are generalizable to all populations (Thomas, 2011 ). Comparisons between case study and statistical research do little to advance this qualitative approach, and fail to recognize its inherent value, which can be better understood from the interpretive or social constructionist viewpoint of other authors (Merriam, 2009 ; Stake, 1995 ). Building on discussions relating to “fuzzy” (Bassey, 2001 ), or naturalistic generalizations (Stake, 1978 ), or transference of concepts and theories (Ayres, Kavanaugh, & Knafl, 2003 ; Morse et al., 2011 ) would have more relevance.

Case study research has been used as a catch-all design to justify or add weight to fundamental qualitative descriptive studies that do not fit with other traditional frameworks (Merriam, 2009 ). A case study has been a “convenient label for our research—when we ‘can't think of anything ‘better”—in an attempt to give it [qualitative methodology] some added respectability” (Tight, 2010 , p. 337). Qualitative case study research is a pliable approach (Merriam, 2009 ; Meyer, 2001 ; Stake, 1995 ), and has been likened to a “curious methodological limbo” (Gerring, 2004 , p. 341) or “paradigmatic bridge” (Luck et al., 2006 , p. 104), that is on the borderline between postpositivist and constructionist interpretations. This has resulted in inconsistency in application, which indicates that flexibility comes with limitations (Meyer, 2001 ), and the open nature of case study research might be off-putting to novice researchers (Thomas, 2011 ). The development of a well-(in)formed theoretical framework to guide a case study should improve consistency, rigour, and trust in studies published in qualitative research journals (Meyer, 2001 ).

Assessment of rigour

The purpose of this study was to analyse the methodological descriptions of case studies published in qualitative methods journals. To do this we needed to develop a suitable framework, which used existing, established criteria for appraising qualitative case study research rigour (Creswell, 2013b ; Merriam, 2009 ; Stake, 1995 ). A number of qualitative authors have developed concepts and criteria that are used to determine whether a study is rigorous (Denzin & Lincoln, 2011b ; Lincoln, 1995 ; Sandelowski & Barroso, 2002 ). The criteria proposed by Stake ( 1995 ) provide a framework for readers and reviewers to make judgements regarding case study quality, and identify key characteristics essential for good methodological rigour. Although each of the factors listed in Stake's criteria could enhance the quality of a qualitative research report, in Table I we present an adapted criteria used in this study, which integrates more recent work by Merriam ( 2009 ) and Creswell ( 2013b ). Stake's ( 1995 ) original criteria were separated into two categories. The first list of general criteria is “relevant for all qualitative research.” The second list, “high relevance to qualitative case study research,” was the criteria that we decided had higher relevance to case study research. This second list was the main criteria used to assess the methodological descriptions of the case studies reviewed. The complete table has been preserved so that the reader can determine how the original criteria were adapted.

Framework for assessing quality in qualitative case study research.

Adapted from Stake ( 1995 , p. 131).

Study design

The critical review method described by Grant and Booth ( 2009 ) was used, which is appropriate for the assessment of research quality, and is used for literature analysis to inform research and practice. This type of review goes beyond the mapping and description of scoping or rapid reviews, to include “analysis and conceptual innovation” (Grant & Booth, 2009 , p. 93). A critical review is used to develop existing, or produce new, hypotheses or models. This is different to systematic reviews that answer clinical questions. It is used to evaluate existing research and competing ideas, to provide a “launch pad” for conceptual development and “subsequent testing” (Grant & Booth, 2009 , p. 93).

Qualitative methods journals were located by a search of the 2011 ISI Journal Citation Reports in Social Science, via the database Web of Knowledge (see m.webofknowledge.com). No “qualitative research methods” category existed in the citation reports; therefore, a search of all categories was performed using the term “qualitative.” In Table II , we present the qualitative methods journals located, ranked by impact factor. The highest ranked journals were selected for searching. We acknowledge that the impact factor ranking system might not be the best measure of journal quality (Cheek, Garnham, & Quan, 2006 ); however, this was the most appropriate and accessible method available.

International Journal of Qualitative Studies on Health and Well-being.

Search strategy

In March 2013, searches of the journals, Qualitative Health Research , Qualitative Research , and Qualitative Inquiry were completed to retrieve studies with “case study” in the abstract field. The search was limited to the past 5 years (1 January 2008 to 1 March 2013). The objective was to locate published qualitative case studies suitable for assessment using the adapted criterion. Viewpoints, commentaries, and other article types were excluded from review. Title and abstracts of the 45 retrieved articles were read by the first author, who identified 34 empirical case studies for review. All authors reviewed the 34 studies to confirm selection and categorization. In Table III , we present the 34 case studies grouped by journal, and categorized by research topic, including health sciences, social sciences and anthropology, and methods research. There was a discrepancy in categorization of one article on pedagogy and a new teaching method published in Qualitative Inquiry (Jorrín-Abellán, Rubia-Avi, Anguita-Martínez, Gómez-Sánchez, & Martínez-Mones, 2008 ). Consensus was to allocate to the methods category.

Outcomes of search of qualitative methods journals.

In Table III , the number of studies located, and final numbers selected for review have been reported. Qualitative Health Research published the most empirical case studies ( n= 16). In the health category, there were 12 case studies of health conditions, health services, and health policy issues, all published in Qualitative Health Research . Seven case studies were categorized as social sciences and anthropology research, which combined case study with biography and ethnography methodologies. All three journals published case studies on methods research to illustrate a data collection or analysis technique, methodological procedure, or related issue.

The methodological descriptions of 34 case studies were critically reviewed using the adapted criteria. All articles reviewed contained a description of study methods; however, the length, amount of detail, and position of the description in the article varied. Few studies provided an accurate description and rationale for using a qualitative case study approach. In the 34 case studies reviewed, three described a theoretical framework informed by Stake ( 1995 ), two by Yin ( 2009 ), and three provided a mixed framework informed by various authors, which might have included both Yin and Stake. Few studies described their case study design, or included a rationale that explained why they excluded or added further procedures, and whether this was to enhance the study design, or to better suit the research question. In 26 of the studies no reference was provided to principal case study authors. From reviewing the description of methods, few authors provided a description or justification of case study methodology that demonstrated how their study was informed by the methodological literature that exists on this approach.

The methodological descriptions of each study were reviewed using the adapted criteria, and the following issues were identified: case study methodology or method; case of something particular and case selection; contextually bound case study; researcher and case interactions and triangulation; and, study design inconsistent with methodology. An outline of how the issues were developed from the critical review is provided, followed by a discussion of how these relate to the current methodological literature.

Case study methodology or method

A third of the case studies reviewed appeared to use a case report method, not case study methodology as described by principal authors (Creswell, 2013b ; Merriam, 2009 ; Stake, 1995 ; Yin, 2009 ). Case studies were identified as a case report because of missing methodological detail and by review of the study aims and purpose. These reports presented data for small samples of no more than three people, places or phenomenon. Four studies, or “case reports” were single cases selected retrospectively from larger studies (Bronken, Kirkevold, Martinsen, & Kvigne, 2012 ; Coltart & Henwood, 2012 ; Hooghe, Neimeyer, & Rober, 2012 ; Roscigno et al., 2012 ). Case reports were not a case of something, instead were a case demonstration or an example presented in a report. These reports presented outcomes, and reported on how the case could be generalized. Descriptions focussed on the phenomena, rather than the case itself, and did not appear to study the case in its entirety.

Case reports had minimal in-text references to case study methodology, and were informed by other qualitative traditions or secondary sources (Adamson & Holloway, 2012 ; Buzzanell & D'Enbeau, 2009 ; Nagar-Ron & Motzafi-Haller, 2011 ). This does not suggest that case study methodology cannot be multimethod, however, methodology should be consistent in design, be clearly described (Meyer, 2001 ; Stake, 1995 ), and maintain focus on the case (Creswell, 2013b ).

To demonstrate how case reports were identified, three examples are provided. The first, Yeh ( 2013 ) described their study as, “the examination of the emergence of vegetarianism in Victorian England serves as a case study to reveal the relationships between boundaries and entities” (p. 306). The findings were a historical case report, which resulted from an ethnographic study of vegetarianism. Cunsolo Willox, Harper, Edge, ‘My Word’: Storytelling and Digital Media Lab, and Rigolet Inuit Community Government (2013) used “a case study that illustrates the usage of digital storytelling within an Inuit community” (p. 130). This case study reported how digital storytelling can be used with indigenous communities as a participatory method to illuminate the benefits of this method for other studies. This “case study was conducted in the Inuit community” but did not include the Inuit community in case analysis (Cunsolo Willox et al., 2013 , p. 130). Bronken et al. ( 2012 ) provided a single case report to demonstrate issues observed in a larger clinical study of aphasia and stroke, without adequate case description or analysis.

Case study of something particular and case selection

Case selection is a precursor to case analysis, which needs to be presented as a convincing argument (Merriam, 2009 ). Descriptions of the case were often not adequate to ascertain why the case was selected, or whether it was a particular exemplar or outlier (Thomas, 2011 ). In a number of case studies in the health and social science categories, it was not explicit whether the case was of something particular, or peculiar to their discipline or field (Adamson & Holloway, 2012 ; Bronken et al., 2012 ; Colón-Emeric et al., 2010 ; Jackson, Botelho, Welch, Joseph, & Tennstedt, 2012 ; Mawn et al., 2010 ; Snyder-Young, 2011 ). There were exceptions in the methods category ( Table III ), where cases were selected by researchers to report on a new or innovative method. The cases emerged through heuristic study, and were reported to be particular, relative to the existing methods literature (Ajodhia-Andrews & Berman, 2009 ; Buckley & Waring, 2013 ; Cunsolo Willox et al., 2013 ; De Haene, Grietens, & Verschueren, 2010 ; Gratton & O'Donnell, 2011 ; Sumsion, 2013 ; Wimpenny & Savin-Baden, 2012 ).

Case selection processes were sometimes insufficient to understand why the case was selected from the global population of cases, or what study of this case would contribute to knowledge as compared with other possible cases (Adamson & Holloway, 2012 ; Bronken et al., 2012 ; Colón-Emeric et al., 2010 ; Jackson et al., 2012 ; Mawn et al., 2010 ). In two studies, local cases were selected (Barone, 2010 ; Fourie & Theron, 2012 ) because the researcher was familiar with and had access to the case. Possible limitations of a convenience sample were not acknowledged. Purposeful sampling was used to recruit participants within the case of one study, but not of the case itself (Gallagher et al., 2013 ). Random sampling was completed for case selection in two studies (Colón-Emeric et al., 2010 ; Jackson et al., 2012 ), which has limited meaning in interpretive qualitative research.

To demonstrate how researchers provided a good justification for the selection of case study approaches, four examples are provided. The first, cases of residential care homes, were selected because of reported occurrences of mistreatment, which included residents being locked in rooms at night (Rytterström, Unosson, & Arman, 2013 ). Roscigno et al. ( 2012 ) selected cases of parents who were admitted for early hospitalization in neonatal intensive care with a threatened preterm delivery before 26 weeks. Hooghe et al. ( 2012 ) used random sampling to select 20 couples that had experienced the death of a child; however, the case study was of one couple and a particular metaphor described only by them. The final example, Coltart and Henwood ( 2012 ), provided a detailed account of how they selected two cases from a sample of 46 fathers based on personal characteristics and beliefs. They described how the analysis of the two cases would contribute to their larger study on first time fathers and parenting.

Contextually bound case study

The limits or boundaries of the case are a defining factor of case study methodology (Merriam, 2009 ; Ragin & Becker, 1992 ; Stake, 1995 ; Yin, 2009 ). Adequate contextual description is required to understand the setting or context in which the case is revealed. In the health category, case studies were used to illustrate a clinical phenomenon or issue such as compliance and health behaviour (Colón-Emeric et al., 2010 ; D'Enbeau, Buzzanell, & Duckworth, 2010 ; Gallagher et al., 2013 ; Hooghe et al., 2012 ; Jackson et al., 2012 ; Roscigno et al., 2012 ). In these case studies, contextual boundaries, such as physical and institutional descriptions, were not sufficient to understand the case as a holistic system, for example, the general practitioner (GP) clinic in Gallagher et al. ( 2013 ), or the nursing home in Colón-Emeric et al. ( 2010 ). Similarly, in the social science and methods categories, attention was paid to some components of the case context, but not others, missing important information required to understand the case as a holistic system (Alexander, Moreira, & Kumar, 2012 ; Buzzanell & D'Enbeau, 2009 ; Nairn & Panelli, 2009 ; Wimpenny & Savin-Baden, 2012 ).

In two studies, vicarious experience or vignettes (Nairn & Panelli, 2009 ) and images (Jorrín-Abellán et al., 2008 ) were effective to support description of context, and might have been a useful addition for other case studies. Missing contextual boundaries suggests that the case might not be adequately defined. Additional information, such as the physical, institutional, political, and community context, would improve understanding of the case (Stake, 1998 ). In Boxes 1 and 2 , we present brief synopses of two studies that were reviewed, which demonstrated a well bounded case. In Box 1 , Ledderer ( 2011 ) used a qualitative case study design informed by Stake's tradition. In Box 2 , Gillard, Witt, and Watts ( 2011 ) were informed by Yin's tradition. By providing a brief outline of the case studies in Boxes 1 and 2 , we demonstrate how effective case boundaries can be constructed and reported, which may be of particular interest to prospective case study researchers.

Article synopsis of case study research using Stake's tradition

Ledderer ( 2011 ) used a qualitative case study research design, informed by modern ethnography. The study is bounded to 10 general practice clinics in Denmark, who had received federal funding to implement preventative care services based on a Motivational Interviewing intervention. The researcher question focussed on “why is it so difficult to create change in medical practice?” (Ledderer, 2011 , p. 27). The study context was adequately described, providing detail on the general practitioner (GP) clinics and relevant political and economic influences. Methodological decisions are described in first person narrative, providing insight on researcher perspectives and interaction with the case. Forty-four interviews were conducted, which focussed on how GPs conducted consultations, and the form, nature and content, rather than asking their opinion or experience (Ledderer, 2011 , p. 30). The duration and intensity of researcher immersion in the case enhanced depth of description and trustworthiness of study findings. Analysis was consistent with Stake's tradition, and the researcher provided examples of inquiry techniques used to challenge assumptions about emerging themes. Several other seminal qualitative works were cited. The themes and typology constructed are rich in narrative data and storytelling by clinic staff, demonstrating individual clinic experiences as well as shared meanings and understandings about changing from a biomedical to psychological approach to preventative health intervention. Conclusions make note of social and cultural meanings and lessons learned, which might not have been uncovered using a different methodology.

Article synopsis of case study research using Yin's tradition

Gillard et al. ( 2011 ) study of camps for adolescents living with HIV/AIDs provided a good example of Yin's interpretive case study approach. The context of the case is bounded by the three summer camps of which the researchers had prior professional involvement. A case study protocol was developed that used multiple methods to gather information at three data collection points coinciding with three youth camps (Teen Forum, Discover Camp, and Camp Strong). Gillard and colleagues followed Yin's ( 2009 ) principles, using a consistent data protocol that enhanced cross-case analysis. Data described the young people, the camp physical environment, camp schedule, objectives and outcomes, and the staff of three youth camps. The findings provided a detailed description of the context, with less detail of individual participants, including insight into researcher's interpretations and methodological decisions throughout the data collection and analysis process. Findings provided the reader with a sense of “being there,” and are discovered through constant comparison of the case with the research issues; the case is the unit of analysis. There is evidence of researcher immersion in the case, and Gillard reports spending significant time in the field in a naturalistic and integrated youth mentor role.

This case study is not intended to have a significant impact on broader health policy, although does have implications for health professionals working with adolescents. Study conclusions will inform future camps for young people with chronic disease, and practitioners are able to compare similarities between this case and their own practice (for knowledge translation). No limitations of this article were reported. Limitations related to publication of this case study were that it was 20 pages long and used three tables to provide sufficient description of the camp and program components, and relationships with the research issue.

Researcher and case interactions and triangulation

Researcher and case interactions and transactions are a defining feature of case study methodology (Stake, 1995 ). Narrative stories, vignettes, and thick description are used to provoke vicarious experience and a sense of being there with the researcher in their interaction with the case. Few of the case studies reviewed provided details of the researcher's relationship with the case, researcher–case interactions, and how these influenced the development of the case study (Buzzanell & D'Enbeau, 2009 ; D'Enbeau et al., 2010 ; Gallagher et al., 2013 ; Gillard et al., 2011 ; Ledderer, 2011 ; Nagar-Ron & Motzafi-Haller, 2011 ). The role and position of the researcher needed to be self-examined and understood by readers, to understand how this influenced interactions with participants, and to determine what triangulation is needed (Merriam, 2009 ; Stake, 1995 ).

Gillard et al. ( 2011 ) provided a good example of triangulation, comparing data sources in a table (p. 1513). Triangulation of sources was used to reveal as much depth as possible in the study by Nagar-Ron and Motzafi-Haller ( 2011 ), while also enhancing confirmation validity. There were several case studies that would have benefited from improved range and use of data sources, and descriptions of researcher–case interactions (Ajodhia-Andrews & Berman, 2009 ; Bronken et al., 2012 ; Fincham, Scourfield, & Langer, 2008 ; Fourie & Theron, 2012 ; Hooghe et al., 2012 ; Snyder-Young, 2011 ; Yeh, 2013 ).

Study design inconsistent with methodology

Good, rigorous case studies require a strong methodological justification (Meyer, 2001 ) and a logical and coherent argument that defines paradigm, methodological position, and selection of study methods (Denzin & Lincoln, 2011b ). Methodological justification was insufficient in several of the studies reviewed (Barone, 2010 ; Bronken et al., 2012 ; Hooghe et al., 2012 ; Mawn et al., 2010 ; Roscigno et al., 2012 ; Yeh, 2013 ). This was judged by the absence, or inadequate or inconsistent reference to case study methodology in-text.

In six studies, the methodological justification provided did not relate to case study. There were common issues identified. Secondary sources were used as primary methodological references indicating that study design might not have been theoretically sound (Colón-Emeric et al., 2010 ; Coltart & Henwood, 2012 ; Roscigno et al., 2012 ; Snyder-Young, 2011 ). Authors and sources cited in methodological descriptions were inconsistent with the actual study design and practices used (Fourie & Theron, 2012 ; Hooghe et al., 2012 ; Jorrín-Abellán et al., 2008 ; Mawn et al., 2010 ; Rytterström et al., 2013 ; Wimpenny & Savin-Baden, 2012 ). This occurred when researchers cited Stake or Yin, or both (Mawn et al., 2010 ; Rytterström et al., 2013 ), although did not follow their paradigmatic or methodological approach. In 26 studies there were no citations for a case study methodological approach.

The findings of this study have highlighted a number of issues for researchers. A considerable number of case studies reviewed were missing key elements that define qualitative case study methodology and the tradition cited. A significant number of studies did not provide a clear methodological description or justification relevant to case study. Case studies in health and social sciences did not provide sufficient information for the reader to understand case selection, and why this case was chosen above others. The context of the cases were not described in adequate detail to understand all relevant elements of the case context, which indicated that cases may have not been contextually bounded. There were inconsistencies between reported methodology, study design, and paradigmatic approach in case studies reviewed, which made it difficult to understand the study methodology and theoretical foundations. These issues have implications for methodological integrity and honesty when reporting study design, which are values of the qualitative research tradition and are ethical requirements (Wager & Kleinert, 2010a ). Poorly described methodological descriptions may lead the reader to misinterpret or discredit study findings, which limits the impact of the study, and, as a collective, hinders advancements in the broader qualitative research field.

The issues highlighted in our review build on current debates in the case study literature, and queries about the value of this methodology. Case study research can be situated within different paradigms or designed with an array of methods. In order to maintain the creativity and flexibility that is valued in this methodology, clearer descriptions of paradigm and theoretical position and methods should be provided so that study findings are not undervalued or discredited. Case study research is an interdisciplinary practice, which means that clear methodological descriptions might be more important for this approach than other methodologies that are predominantly driven by fewer disciplines (Creswell, 2013b ).

Authors frequently omit elements of methodologies and include others to strengthen study design, and we do not propose a rigid or purist ideology in this paper. On the contrary, we encourage new ideas about using case study, together with adequate reporting, which will advance the value and practice of case study. The implications of unclear methodological descriptions in the studies reviewed were that study design appeared to be inconsistent with reported methodology, and key elements required for making judgements of rigour were missing. It was not clear whether the deviations from methodological tradition were made by researchers to strengthen the study design, or because of misinterpretations. Morse ( 2011 ) recommended that innovations and deviations from practice are best made by experienced researchers, and that a novice might be unaware of the issues involved with making these changes. To perpetuate the tradition of case study research, applications in the published literature should have consistencies with traditional methodological constructions, and deviations should be described with a rationale that is inherent in study conduct and findings. Providing methodological descriptions that demonstrate a strong theoretical foundation and coherent study design will add credibility to the study, while ensuring the intrinsic meaning of case study is maintained.

The value of this review is that it contributes to discussion of whether case study is a methodology or method. We propose possible reasons why researchers might make this misinterpretation. Researchers may interchange the terms methods and methodology, and conduct research without adequate attention to epistemology and historical tradition (Carter & Little, 2007 ; Sandelowski, 2010 ). If the rich meaning that naming a qualitative methodology brings to the study is not recognized, a case study might appear to be inconsistent with the traditional approaches described by principal authors (Creswell, 2013a ; Merriam, 2009 ; Stake, 1995 ; Yin, 2009 ). If case studies are not methodologically and theoretically situated, then they might appear to be a case report.

Case reports are promoted by university and medical journals as a method of reporting on medical or scientific cases; guidelines for case reports are publicly available on websites ( http://www.hopkinsmedicine.org/institutional_review_board/guidelines_policies/guidelines/case_report.html ). The various case report guidelines provide a general criteria for case reports, which describes that this form of report does not meet the criteria of research, is used for retrospective analysis of up to three clinical cases, and is primarily illustrative and for educational purposes. Case reports can be published in academic journals, but do not require approval from a human research ethics committee. Traditionally, case reports describe a single case, to explain how and what occurred in a selected setting, for example, to illustrate a new phenomenon that has emerged from a larger study. A case report is not necessarily particular or the study of a case in its entirety, and the larger study would usually be guided by a different research methodology.

This description of a case report is similar to what was provided in some studies reviewed. This form of report lacks methodological grounding and qualities of research rigour. The case report has publication value in demonstrating an example and for dissemination of knowledge (Flanagan, 1999 ). However, case reports have different meaning and purpose to case study, which needs to be distinguished. Findings of our review suggest that the medical understanding of a case report has been confused with qualitative case study approaches.

In this review, a number of case studies did not have methodological descriptions that included key characteristics of case study listed in the adapted criteria, and several issues have been discussed. There have been calls for improvements in publication quality of qualitative research (Morse, 2011 ), and for improvements in peer review of submitted manuscripts (Carter & Little, 2007 ; Jasper, Vaismoradi, Bondas, & Turunen, 2013 ). The challenging nature of editor and reviewers responsibilities are acknowledged in the literature (Hames, 2013 ; Wager & Kleinert, 2010b ); however, review of case study methodology should be prioritized because of disputes on methodological value.

Authors using case study approaches are recommended to describe their theoretical framework and methods clearly, and to seek and follow specialist methodological advice when needed (Wager & Kleinert, 2010a ). Adequate page space for case study description would contribute to better publications (Gillard et al., 2011 ). Capitalizing on the ability to publish complementary resources should be considered.

Limitations of the review

There is a level of subjectivity involved in this type of review and this should be considered when interpreting study findings. Qualitative methods journals were selected because the aims and scope of these journals are to publish studies that contribute to methodological discussion and development of qualitative research. Generalist health and social science journals were excluded that might have contained good quality case studies. Journals in business or education were also excluded, although a review of case studies in international business journals has been published elsewhere (Piekkari et al., 2009 ).

The criteria used to assess the quality of the case studies were a set of qualitative indicators. A numerical or ranking system might have resulted in different results. Stake's ( 1995 ) criteria have been referenced elsewhere, and was deemed the best available (Creswell, 2013b ; Crowe et al., 2011 ). Not all qualitative studies are reported in a consistent way and some authors choose to report findings in a narrative form in comparison to a typical biomedical report style (Sandelowski & Barroso, 2002 ), if misinterpretations were made this may have affected the review.

Case study research is an increasingly popular approach among qualitative researchers, which provides methodological flexibility through the incorporation of different paradigmatic positions, study designs, and methods. However, whereas flexibility can be an advantage, a myriad of different interpretations has resulted in critics questioning the use of case study as a methodology. Using an adaptation of established criteria, we aimed to identify and assess the methodological descriptions of case studies in high impact, qualitative methods journals. Few articles were identified that applied qualitative case study approaches as described by experts in case study design. There were inconsistencies in methodology and study design, which indicated that researchers were confused whether case study was a methodology or a method. Commonly, there appeared to be confusion between case studies and case reports. Without clear understanding and application of the principles and key elements of case study methodology, there is a risk that the flexibility of the approach will result in haphazard reporting, and will limit its global application as a valuable, theoretically supported methodology that can be rigorously applied across disciplines and fields.

Conflict of interest and funding

The authors have not received any funding or benefits from industry or elsewhere to conduct this study.

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• Open access
• Published: 27 June 2011

The case study approach

• Sarah Crowe 1 ,
• Kathrin Cresswell 2 ,
• Ann Robertson 2 ,
• Guro Huby 3 ,
• Anthony Avery 1 &
• Aziz Sheikh 2  

BMC Medical Research Methodology volume  11 , Article number:  100 ( 2011 ) Cite this article

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The case study approach allows in-depth, multi-faceted explorations of complex issues in their real-life settings. The value of the case study approach is well recognised in the fields of business, law and policy, but somewhat less so in health services research. Based on our experiences of conducting several health-related case studies, we reflect on the different types of case study design, the specific research questions this approach can help answer, the data sources that tend to be used, and the particular advantages and disadvantages of employing this methodological approach. The paper concludes with key pointers to aid those designing and appraising proposals for conducting case study research, and a checklist to help readers assess the quality of case study reports.

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Introduction

The case study approach is particularly useful to employ when there is a need to obtain an in-depth appreciation of an issue, event or phenomenon of interest, in its natural real-life context. Our aim in writing this piece is to provide insights into when to consider employing this approach and an overview of key methodological considerations in relation to the design, planning, analysis, interpretation and reporting of case studies.

The illustrative 'grand round', 'case report' and 'case series' have a long tradition in clinical practice and research. Presenting detailed critiques, typically of one or more patients, aims to provide insights into aspects of the clinical case and, in doing so, illustrate broader lessons that may be learnt. In research, the conceptually-related case study approach can be used, for example, to describe in detail a patient's episode of care, explore professional attitudes to and experiences of a new policy initiative or service development or more generally to 'investigate contemporary phenomena within its real-life context' [ 1 ]. Based on our experiences of conducting a range of case studies, we reflect on when to consider using this approach, discuss the key steps involved and illustrate, with examples, some of the practical challenges of attaining an in-depth understanding of a 'case' as an integrated whole. In keeping with previously published work, we acknowledge the importance of theory to underpin the design, selection, conduct and interpretation of case studies[ 2 ]. In so doing, we make passing reference to the different epistemological approaches used in case study research by key theoreticians and methodologists in this field of enquiry.

This paper is structured around the following main questions: What is a case study? What are case studies used for? How are case studies conducted? What are the potential pitfalls and how can these be avoided? We draw in particular on four of our own recently published examples of case studies (see Tables 1 , 2 , 3 and 4 ) and those of others to illustrate our discussion[ 3 – 7 ].

What is a case study?

A case study is a research approach that is used to generate an in-depth, multi-faceted understanding of a complex issue in its real-life context. It is an established research design that is used extensively in a wide variety of disciplines, particularly in the social sciences. A case study can be defined in a variety of ways (Table 5 ), the central tenet being the need to explore an event or phenomenon in depth and in its natural context. It is for this reason sometimes referred to as a "naturalistic" design; this is in contrast to an "experimental" design (such as a randomised controlled trial) in which the investigator seeks to exert control over and manipulate the variable(s) of interest.

Stake's work has been particularly influential in defining the case study approach to scientific enquiry. He has helpfully characterised three main types of case study: intrinsic , instrumental and collective [ 8 ]. An intrinsic case study is typically undertaken to learn about a unique phenomenon. The researcher should define the uniqueness of the phenomenon, which distinguishes it from all others. In contrast, the instrumental case study uses a particular case (some of which may be better than others) to gain a broader appreciation of an issue or phenomenon. The collective case study involves studying multiple cases simultaneously or sequentially in an attempt to generate a still broader appreciation of a particular issue.

These are however not necessarily mutually exclusive categories. In the first of our examples (Table 1 ), we undertook an intrinsic case study to investigate the issue of recruitment of minority ethnic people into the specific context of asthma research studies, but it developed into a instrumental case study through seeking to understand the issue of recruitment of these marginalised populations more generally, generating a number of the findings that are potentially transferable to other disease contexts[ 3 ]. In contrast, the other three examples (see Tables 2 , 3 and 4 ) employed collective case study designs to study the introduction of workforce reconfiguration in primary care, the implementation of electronic health records into hospitals, and to understand the ways in which healthcare students learn about patient safety considerations[ 4 – 6 ]. Although our study focusing on the introduction of General Practitioners with Specialist Interests (Table 2 ) was explicitly collective in design (four contrasting primary care organisations were studied), is was also instrumental in that this particular professional group was studied as an exemplar of the more general phenomenon of workforce redesign[ 4 ].

What are case studies used for?

According to Yin, case studies can be used to explain, describe or explore events or phenomena in the everyday contexts in which they occur[ 1 ]. These can, for example, help to understand and explain causal links and pathways resulting from a new policy initiative or service development (see Tables 2 and 3 , for example)[ 1 ]. In contrast to experimental designs, which seek to test a specific hypothesis through deliberately manipulating the environment (like, for example, in a randomised controlled trial giving a new drug to randomly selected individuals and then comparing outcomes with controls),[ 9 ] the case study approach lends itself well to capturing information on more explanatory ' how ', 'what' and ' why ' questions, such as ' how is the intervention being implemented and received on the ground?'. The case study approach can offer additional insights into what gaps exist in its delivery or why one implementation strategy might be chosen over another. This in turn can help develop or refine theory, as shown in our study of the teaching of patient safety in undergraduate curricula (Table 4 )[ 6 , 10 ]. Key questions to consider when selecting the most appropriate study design are whether it is desirable or indeed possible to undertake a formal experimental investigation in which individuals and/or organisations are allocated to an intervention or control arm? Or whether the wish is to obtain a more naturalistic understanding of an issue? The former is ideally studied using a controlled experimental design, whereas the latter is more appropriately studied using a case study design.

Case studies may be approached in different ways depending on the epistemological standpoint of the researcher, that is, whether they take a critical (questioning one's own and others' assumptions), interpretivist (trying to understand individual and shared social meanings) or positivist approach (orientating towards the criteria of natural sciences, such as focusing on generalisability considerations) (Table 6 ). Whilst such a schema can be conceptually helpful, it may be appropriate to draw on more than one approach in any case study, particularly in the context of conducting health services research. Doolin has, for example, noted that in the context of undertaking interpretative case studies, researchers can usefully draw on a critical, reflective perspective which seeks to take into account the wider social and political environment that has shaped the case[ 11 ].

How are case studies conducted?

Here, we focus on the main stages of research activity when planning and undertaking a case study; the crucial stages are: defining the case; selecting the case(s); collecting and analysing the data; interpreting data; and reporting the findings.

Defining the case

Carefully formulated research question(s), informed by the existing literature and a prior appreciation of the theoretical issues and setting(s), are all important in appropriately and succinctly defining the case[ 8 , 12 ]. Crucially, each case should have a pre-defined boundary which clarifies the nature and time period covered by the case study (i.e. its scope, beginning and end), the relevant social group, organisation or geographical area of interest to the investigator, the types of evidence to be collected, and the priorities for data collection and analysis (see Table 7 )[ 1 ]. A theory driven approach to defining the case may help generate knowledge that is potentially transferable to a range of clinical contexts and behaviours; using theory is also likely to result in a more informed appreciation of, for example, how and why interventions have succeeded or failed[ 13 ].

For example, in our evaluation of the introduction of electronic health records in English hospitals (Table 3 ), we defined our cases as the NHS Trusts that were receiving the new technology[ 5 ]. Our focus was on how the technology was being implemented. However, if the primary research interest had been on the social and organisational dimensions of implementation, we might have defined our case differently as a grouping of healthcare professionals (e.g. doctors and/or nurses). The precise beginning and end of the case may however prove difficult to define. Pursuing this same example, when does the process of implementation and adoption of an electronic health record system really begin or end? Such judgements will inevitably be influenced by a range of factors, including the research question, theory of interest, the scope and richness of the gathered data and the resources available to the research team.

Selecting the case(s)

The decision on how to select the case(s) to study is a very important one that merits some reflection. In an intrinsic case study, the case is selected on its own merits[ 8 ]. The case is selected not because it is representative of other cases, but because of its uniqueness, which is of genuine interest to the researchers. This was, for example, the case in our study of the recruitment of minority ethnic participants into asthma research (Table 1 ) as our earlier work had demonstrated the marginalisation of minority ethnic people with asthma, despite evidence of disproportionate asthma morbidity[ 14 , 15 ]. In another example of an intrinsic case study, Hellstrom et al.[ 16 ] studied an elderly married couple living with dementia to explore how dementia had impacted on their understanding of home, their everyday life and their relationships.

For an instrumental case study, selecting a "typical" case can work well[ 8 ]. In contrast to the intrinsic case study, the particular case which is chosen is of less importance than selecting a case that allows the researcher to investigate an issue or phenomenon. For example, in order to gain an understanding of doctors' responses to health policy initiatives, Som undertook an instrumental case study interviewing clinicians who had a range of responsibilities for clinical governance in one NHS acute hospital trust[ 17 ]. Sampling a "deviant" or "atypical" case may however prove even more informative, potentially enabling the researcher to identify causal processes, generate hypotheses and develop theory.

In collective or multiple case studies, a number of cases are carefully selected. This offers the advantage of allowing comparisons to be made across several cases and/or replication. Choosing a "typical" case may enable the findings to be generalised to theory (i.e. analytical generalisation) or to test theory by replicating the findings in a second or even a third case (i.e. replication logic)[ 1 ]. Yin suggests two or three literal replications (i.e. predicting similar results) if the theory is straightforward and five or more if the theory is more subtle. However, critics might argue that selecting 'cases' in this way is insufficiently reflexive and ill-suited to the complexities of contemporary healthcare organisations.

The selected case study site(s) should allow the research team access to the group of individuals, the organisation, the processes or whatever else constitutes the chosen unit of analysis for the study. Access is therefore a central consideration; the researcher needs to come to know the case study site(s) well and to work cooperatively with them. Selected cases need to be not only interesting but also hospitable to the inquiry [ 8 ] if they are to be informative and answer the research question(s). Case study sites may also be pre-selected for the researcher, with decisions being influenced by key stakeholders. For example, our selection of case study sites in the evaluation of the implementation and adoption of electronic health record systems (see Table 3 ) was heavily influenced by NHS Connecting for Health, the government agency that was responsible for overseeing the National Programme for Information Technology (NPfIT)[ 5 ]. This prominent stakeholder had already selected the NHS sites (through a competitive bidding process) to be early adopters of the electronic health record systems and had negotiated contracts that detailed the deployment timelines.

It is also important to consider in advance the likely burden and risks associated with participation for those who (or the site(s) which) comprise the case study. Of particular importance is the obligation for the researcher to think through the ethical implications of the study (e.g. the risk of inadvertently breaching anonymity or confidentiality) and to ensure that potential participants/participating sites are provided with sufficient information to make an informed choice about joining the study. The outcome of providing this information might be that the emotive burden associated with participation, or the organisational disruption associated with supporting the fieldwork, is considered so high that the individuals or sites decide against participation.

In our example of evaluating implementations of electronic health record systems, given the restricted number of early adopter sites available to us, we sought purposively to select a diverse range of implementation cases among those that were available[ 5 ]. We chose a mixture of teaching, non-teaching and Foundation Trust hospitals, and examples of each of the three electronic health record systems procured centrally by the NPfIT. At one recruited site, it quickly became apparent that access was problematic because of competing demands on that organisation. Recognising the importance of full access and co-operative working for generating rich data, the research team decided not to pursue work at that site and instead to focus on other recruited sites.

Collecting the data

In order to develop a thorough understanding of the case, the case study approach usually involves the collection of multiple sources of evidence, using a range of quantitative (e.g. questionnaires, audits and analysis of routinely collected healthcare data) and more commonly qualitative techniques (e.g. interviews, focus groups and observations). The use of multiple sources of data (data triangulation) has been advocated as a way of increasing the internal validity of a study (i.e. the extent to which the method is appropriate to answer the research question)[ 8 , 18 – 21 ]. An underlying assumption is that data collected in different ways should lead to similar conclusions, and approaching the same issue from different angles can help develop a holistic picture of the phenomenon (Table 2 )[ 4 ].

Brazier and colleagues used a mixed-methods case study approach to investigate the impact of a cancer care programme[ 22 ]. Here, quantitative measures were collected with questionnaires before, and five months after, the start of the intervention which did not yield any statistically significant results. Qualitative interviews with patients however helped provide an insight into potentially beneficial process-related aspects of the programme, such as greater, perceived patient involvement in care. The authors reported how this case study approach provided a number of contextual factors likely to influence the effectiveness of the intervention and which were not likely to have been obtained from quantitative methods alone.

In collective or multiple case studies, data collection needs to be flexible enough to allow a detailed description of each individual case to be developed (e.g. the nature of different cancer care programmes), before considering the emerging similarities and differences in cross-case comparisons (e.g. to explore why one programme is more effective than another). It is important that data sources from different cases are, where possible, broadly comparable for this purpose even though they may vary in nature and depth.

Analysing, interpreting and reporting case studies

Making sense and offering a coherent interpretation of the typically disparate sources of data (whether qualitative alone or together with quantitative) is far from straightforward. Repeated reviewing and sorting of the voluminous and detail-rich data are integral to the process of analysis. In collective case studies, it is helpful to analyse data relating to the individual component cases first, before making comparisons across cases. Attention needs to be paid to variations within each case and, where relevant, the relationship between different causes, effects and outcomes[ 23 ]. Data will need to be organised and coded to allow the key issues, both derived from the literature and emerging from the dataset, to be easily retrieved at a later stage. An initial coding frame can help capture these issues and can be applied systematically to the whole dataset with the aid of a qualitative data analysis software package.

The Framework approach is a practical approach, comprising of five stages (familiarisation; identifying a thematic framework; indexing; charting; mapping and interpretation) , to managing and analysing large datasets particularly if time is limited, as was the case in our study of recruitment of South Asians into asthma research (Table 1 )[ 3 , 24 ]. Theoretical frameworks may also play an important role in integrating different sources of data and examining emerging themes. For example, we drew on a socio-technical framework to help explain the connections between different elements - technology; people; and the organisational settings within which they worked - in our study of the introduction of electronic health record systems (Table 3 )[ 5 ]. Our study of patient safety in undergraduate curricula drew on an evaluation-based approach to design and analysis, which emphasised the importance of the academic, organisational and practice contexts through which students learn (Table 4 )[ 6 ].

Case study findings can have implications both for theory development and theory testing. They may establish, strengthen or weaken historical explanations of a case and, in certain circumstances, allow theoretical (as opposed to statistical) generalisation beyond the particular cases studied[ 12 ]. These theoretical lenses should not, however, constitute a strait-jacket and the cases should not be "forced to fit" the particular theoretical framework that is being employed.

When reporting findings, it is important to provide the reader with enough contextual information to understand the processes that were followed and how the conclusions were reached. In a collective case study, researchers may choose to present the findings from individual cases separately before amalgamating across cases. Care must be taken to ensure the anonymity of both case sites and individual participants (if agreed in advance) by allocating appropriate codes or withholding descriptors. In the example given in Table 3 , we decided against providing detailed information on the NHS sites and individual participants in order to avoid the risk of inadvertent disclosure of identities[ 5 , 25 ].

What are the potential pitfalls and how can these be avoided?

The case study approach is, as with all research, not without its limitations. When investigating the formal and informal ways undergraduate students learn about patient safety (Table 4 ), for example, we rapidly accumulated a large quantity of data. The volume of data, together with the time restrictions in place, impacted on the depth of analysis that was possible within the available resources. This highlights a more general point of the importance of avoiding the temptation to collect as much data as possible; adequate time also needs to be set aside for data analysis and interpretation of what are often highly complex datasets.

Case study research has sometimes been criticised for lacking scientific rigour and providing little basis for generalisation (i.e. producing findings that may be transferable to other settings)[ 1 ]. There are several ways to address these concerns, including: the use of theoretical sampling (i.e. drawing on a particular conceptual framework); respondent validation (i.e. participants checking emerging findings and the researcher's interpretation, and providing an opinion as to whether they feel these are accurate); and transparency throughout the research process (see Table 8 )[ 8 , 18 – 21 , 23 , 26 ]. Transparency can be achieved by describing in detail the steps involved in case selection, data collection, the reasons for the particular methods chosen, and the researcher's background and level of involvement (i.e. being explicit about how the researcher has influenced data collection and interpretation). Seeking potential, alternative explanations, and being explicit about how interpretations and conclusions were reached, help readers to judge the trustworthiness of the case study report. Stake provides a critique checklist for a case study report (Table 9 )[ 8 ].

Conclusions

The case study approach allows, amongst other things, critical events, interventions, policy developments and programme-based service reforms to be studied in detail in a real-life context. It should therefore be considered when an experimental design is either inappropriate to answer the research questions posed or impossible to undertake. Considering the frequency with which implementations of innovations are now taking place in healthcare settings and how well the case study approach lends itself to in-depth, complex health service research, we believe this approach should be more widely considered by researchers. Though inherently challenging, the research case study can, if carefully conceptualised and thoughtfully undertaken and reported, yield powerful insights into many important aspects of health and healthcare delivery.

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Acknowledgements

We are grateful to the participants and colleagues who contributed to the individual case studies that we have drawn on. This work received no direct funding, but it has been informed by projects funded by Asthma UK, the NHS Service Delivery Organisation, NHS Connecting for Health Evaluation Programme, and Patient Safety Research Portfolio. We would also like to thank the expert reviewers for their insightful and constructive feedback. Our thanks are also due to Dr. Allison Worth who commented on an earlier draft of this manuscript.

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Case Study Method: Definition, Research Types, Advantages

by  Antony W

May 29, 2024

Case study method, or simply case study research methodology, is a technique that employs investigative inquiry to get data from specific individuals, organizations, groups, events, or demography.

Every participant in a case study method gets a similar engagement with hopes that he or she will provide information that helps with the discovery of novel insights on patterns, ideas, or hypothesis.

What’s The Origin of Case Study Method?

Frederic Le Play in France developed the case study method in sociology in 1829. Field workers would stay with families for a specific time and gather significant data such as income, expenditure, and interaction to understand the family in question.

The case study method was equally popular in clinical medicine, as it helped to generate, analyze, and support hypotheses .

Researchers adapted and integrated the technique to other sectors because of the benefits it uncovered in sociology, anthropology, and clinical medicine. The technique allows for the analysis of outcome through suggested decisions, procedures, and outcomes. 

What Research Types are Used in Case Study Method?

Your case study can be collective, descriptive, exploratory, explanatory, instrumental, or intrinsic.

These case study types require a comprehensive research methodology, which refers to procedures and techniques used to process and evaluate data to solve a problem and achieve a specific goal.

There are 2 types of research approaches for case studies: qualitative and quantitative research . These methods focus on different goals, data, and study.

Qualitative Research for Case Study

Qualitative research focuses on the collection and analysis of non-numerical data and it mostly applies to health sciences, anthropology, history, sociology, and education.

Examples of non-numerical data include audio, text, and video. You can collect qualitative data from focus groups, interviews, surveys, and observations.

Qualitative research for case studies enables you to generate new ideas and helpful insights with relevance and meaning.

Quantitative Research for Case Study

Quantitative research focuses on the collection and analysis of numbers, and it’s common in marketing, psychology, political science, economics, and sociology. Researchers use qualitative research to measure relationships and to test and track averages and patterns.

To do a comprehensive quantitative research:

• Come up with a theory.
• Develop a hypothesis.
• Create a research pattern.
• Operationalize a concept.
• Find a research environment (site).
• Choose your responders.
• Gather, process, and analyze data.
• Record your key findings and publish the results.

What are the Advantages of Case Study Methodology?

The following are the six advantages of the case study methodology:

1. Detailed Examination of a Specific Unit

The case study method enables researchers to document independently verifiable data from firsthand observations. The results provide information on the input mechanism that contributes to a proposed explanation under consideration.

2. Formation of Hypothesis

Researchers use the case study method to test a proposed hypothesis . More often than not, the information acquired from the study may inspire the formation of new concepts and allow further research because it supports change in social and physical settings.

You may collect a comprehensive data set depending on your ability and the openness of the study participants.

3. Constant Examination of Facts

You can use the case study methodology to examine facts about a social group continuously. The constant examination of facts ensures no disruption compromises the authenticity of the data obtained for the project.

Here, researchers don’t need to make assumptions when making conclusions from the collected data, thus ensuring the long-term validity of the findings. The conclusion made becomes significant to both sides of the equation, as it may confirm or reject the theory under investigation.

The constant examination of facts in case study methodology is subject to inefficiency because of the sheer volume of data under examination. Therefore, researchers have the responsibility to determine what information is helpful and what is insignificant.

4. Case Study Method Supports Comparison

Every demographic thinks, behaves, and responds to stimuli in unique ways, but each member of the group will contribute a little portion to a whole. Ideally, individual insights from different settings are a culmination of unique human experiences.

In this case, the case study method allows researchers to compare information from each demographic group, leading to ideas that either support or disapprove a theory.

5. Support for Knowledge Expansion

Researchers can use the case study methodology to expand their knowledge through analysis thanks to the range of methods used to collect data and evaluate hypothesis.

Many researchers collect data from interviews and observations, but even surveys can be just as useful. They may record participants’ experiences and use the information to analyze behavior and decisions. In some instances, a researcher may use memory test and experimental activities to predict how social groups would interact with or respond to given situations.

The information collected then serves to confirm the hypothesized possibilities.

6. Data Sampling Isn’t a Requirement

The case study method looks at social units holistically rather than isolating and analyzing individual data pieces. Therefore, the technique doesn’t require any sampling. The case study method supports the proposition under examination, as it transforms views into facts by validating or rejecting ideas that outside observers may use.

You may heed to specific incidences or results based on broader behavior or concepts. However, the study itself will not sample such instance. The methodology looks at the larger picture instead.

Where Can I Get Help With Case Study Writing?

You can get help with case study writing from Help for Assessment. We have the best case study writers who are only a click away to get you the writing you need to complete your paper on time.

It doesn’t matter if your deadline is closing in or you haven’t started working on the project yet. We can take you from a completely blank page to a well-written document before your due date. 

Help for Assessment charges $12.99 to $40 per page depending on the urgency. You get up to 10% discount if you’re new to this platform. So you can save money and still benefit from the convenience of our custom writing.

About the author 

Antony W is a professional writer and coach at Help for Assessment. He spends countless hours every day researching and writing great content filled with expert advice on how to write engaging essays, research papers, and assignments.

Home » Pros and Cons » 12 Case Study Method Advantages and Disadvantages

12 Case Study Method Advantages and Disadvantages

A case study is an investigation into an individual circumstance. The investigation may be of a single person, business, event, or group. The investigation involves collecting in-depth data about the individual entity through the use of several collection methods. Interviews and observation are two of the most common forms of data collection used.

The case study method was originally developed in the field of clinical medicine. It has expanded since to other industries to examine key results, either positive or negative, that were received through a specific set of decisions. This allows for the topic to be researched with great detail, allowing others to glean knowledge from the information presented.

Here are the advantages and disadvantages of using the case study method.

List of the Advantages of the Case Study Method

1. it turns client observations into useable data..

Case studies offer verifiable data from direct observations of the individual entity involved. These observations provide information about input processes. It can show the path taken which led to specific results being generated. Those observations make it possible for others, in similar circumstances, to potentially replicate the results discovered by the case study method.

2. It turns opinion into fact.

Case studies provide facts to study because you’re looking at data which was generated in real-time. It is a way for researchers to turn their opinions into information that can be verified as fact because there is a proven path of positive or negative development. Singling out a specific incident also provides in-depth details about the path of development, which gives it extra credibility to the outside observer.

3. It is relevant to all parties involved.

Case studies that are chosen well will be relevant to everyone who is participating in the process. Because there is such a high level of relevance involved, researchers are able to stay actively engaged in the data collection process. Participants are able to further their knowledge growth because there is interest in the outcome of the case study. Most importantly, the case study method essentially forces people to make a decision about the question being studied, then defend their position through the use of facts.

4. It uses a number of different research methodologies.

The case study method involves more than just interviews and direct observation. Case histories from a records database can be used with this method. Questionnaires can be distributed to participants in the entity being studies. Individuals who have kept diaries and journals about the entity being studied can be included. Even certain experimental tasks, such as a memory test, can be part of this research process.

5. It can be done remotely.

Researchers do not need to be present at a specific location or facility to utilize the case study method. Research can be obtained over the phone, through email, and other forms of remote communication. Even interviews can be conducted over the phone. That means this method is good for formative research that is exploratory in nature, even if it must be completed from a remote location.

6. It is inexpensive.

Compared to other methods of research, the case study method is rather inexpensive. The costs associated with this method involve accessing data, which can often be done for free. Even when there are in-person interviews or other on-site duties involved, the costs of reviewing the data are minimal.

7. It is very accessible to readers.

The case study method puts data into a usable format for those who read the data and note its outcome. Although there may be perspectives of the researcher included in the outcome, the goal of this method is to help the reader be able to identify specific concepts to which they also relate. That allows them to discover unusual features within the data, examine outliers that may be present, or draw conclusions from their own experiences.

List of the Disadvantages of the Case Study Method

1. it can have influence factors within the data..

Every person has their own unconscious bias. Although the case study method is designed to limit the influence of this bias by collecting fact-based data, it is the collector of the data who gets to define what is a “fact” and what is not. That means the real-time data being collected may be based on the results the researcher wants to see from the entity instead. By controlling how facts are collected, a research can control the results this method generates.

2. It takes longer to analyze the data.

The information collection process through the case study method takes much longer to collect than other research options. That is because there is an enormous amount of data which must be sifted through. It’s not just the researchers who can influence the outcome in this type of research method. Participants can also influence outcomes by given inaccurate or incomplete answers to questions they are asked. Researchers must verify the information presented to ensure its accuracy, and that takes time to complete.

3. It can be an inefficient process.

Case study methods require the participation of the individuals or entities involved for it to be a successful process. That means the skills of the researcher will help to determine the quality of information that is being received. Some participants may be quiet, unwilling to answer even basic questions about what is being studied. Others may be overly talkative, exploring tangents which have nothing to do with the case study at all. If researchers are unsure of how to manage this process, then incomplete data is often collected.

4. It requires a small sample size to be effective.

The case study method requires a small sample size for it to yield an effective amount of data to be analyzed. If there are different demographics involved with the entity, or there are different needs which must be examined, then the case study method becomes very inefficient.

5. It is a labor-intensive method of data collection.

The case study method requires researchers to have a high level of language skills to be successful with data collection. Researchers must be personally involved in every aspect of collecting the data as well. From reviewing files or entries personally to conducting personal interviews, the concepts and themes of this process are heavily reliant on the amount of work each researcher is willing to put into things.

These case study method advantages and disadvantages offer a look at the effectiveness of this research option. With the right skill set, it can be used as an effective tool to gather rich, detailed information about specific entities. Without the right skill set, the case study method becomes inefficient and inaccurate.

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Mar 8 Different Research Methods: Strengths and Weaknesses

By Megan Sumeracki

Image from Pixabay

There are a lot of different methods of conducting research, and each comes with its own set of strengths and weaknesses. I've been thinking a lot about the various research approaches because I'm teaching a senior-level research methods class with a lab this spring. This has led me to think a lot about how these different research methodologies might work together. While most researchers are exposed to a variety of methodologies throughout graduate training, we tend to become engrossed with our own specialty. This makes sense, at least to me, as there are so many nuances that it can take years to become truly proficient in conducting research in our own areas. Specialization seems necessary; however, this is exactly why effective communication and collaboration is key. Given the strengths and weaknesses of different methodologies, a mixed method approach can be used to balance these strengths and weaknesses.

We have said many times before that "it takes a village" and open communication to solve large problems. When it comes to student learning, I feel strongly that it takes a diverse group of experts from different research backgrounds and various experiences teaching in schools. With the amount of time and dedication that it takes to become an expert researcher and an expert teacher, it would be hard for one person to become both! The same is true for research methodologies. There are pros and cons to each, and science is best served when we combine our efforts and tackle our questions from many different directions.

In this spirit, in today's blog I am writing about the general research methodologies that might be used to help us understand student learning. For each methodology, I describe what it is and how it might be used, as well as the strengths and weaknesses of the approach. This blog is a bit longer than our typical blogs because I'm tackling some big topics, but hopefully you'll find the discussion of various research methodologies, together in one place, as important as I do!

Descriptive Research

The main purpose of descriptive research is exactly what it sounds like it should be: to describe what is going on. There are a lot of individual approaches that fall under the descriptive research umbrella. Here are a few:

Case studies are a very in-depth analysis of an individual person, small group of people, or even an event. A researcher might conduct a case study on an individual who has a specific learning disability, or on a classroom that is engaging in a particular mode of instruction. 

Observation research involves sitting back (so to speak) and watching how individuals interact in natural environments. A researcher might (with permission from the school and parents of the children, of course) watch a group of preschoolers through a 2-way mirror to see how the children interact with one another. There is also a special type of observation research called participatory observation . This method is used when it would be difficult or impossible to simply watch from a distance. You can think of this as going under cover, where the researcher joins a group to learn about the group. A classic example involves a researcher, Leon Festinger, who joined a cult who believed the world was going to be destroyed by a flood in the 1950s. From this work, Festinger proposed Cognitive Dissonance Theory (to read more, check out this page ).

Survey research is considered descriptive research. In this work, the researcher compiles a set of questions and asks people to answer these questions. The types of questions can vary. Some surveys might people to rate their feelings or beliefs on a scale from 1-7 (also known as a "Likert" scale) or answer yes-no questions. Some surveys might ask more open-ended questions, and there are many that utilize a mix of these types of questions. If the researcher is asking a lot of open-ended questions, then we might call the research an interview , or a focus group if there are a few people discussing a topic and answering questions in a group. In this research, the participants may actually be guiding the direction of the research.

There is another important distinction to be made under the descriptive research umbrella: quantitative research vs. qualitative research . In quantitative research, data is collected in the forms of numbers. If a researcher asks a student to indicate on a scale from 1-10 how much they think they will remember from a lesson, then we are quantifying the student's perception of their own learning. In qualitative research, words are collected, and sometimes those words might be quantified in some way to use for statistical analysis. If a researcher asks a student to describe their learning process, or conducts in-depth interviews with teachers about classroom learning, then we are dealing with qualitative research.

Descriptive research can provide an in-depth view of any topic we might want to study, and the level of detail that we can find in descriptive research is extremely valuable. This is particularly true of descriptive research that is collected qualitatively. In this form of research, we may find information that we never even knew to look for! This type of research can be used to create new research questions, or form hypotheses about cause and effect relationships (though we cannot determine cause and effect from this research alone). Observation research has an added benefit of allowing us to see how things work in their natural environments. 

Weaknesses:

We cannot determine a cause and effect relationship from descriptive research. For example, if a student talks about engaging with a particular learning strategy, and then provides an in-depth account of why they think it helped them learn, we cannot conclude that this strategy actually did help the student learn.

We also have to be very careful of reactivity in this type of research. Sometimes, people (and animals too) change their behavior if they know they're being observed. Similarly, in surveys we have to worry about participants providing responses that are considered desirable or in line with social norms. (For example, if a parent is asked, "did you ever smoke while pregnant with your child?" we have to worry about parents saying "no, never" because that is the more desirable answer, or the one that aligns with social norms.)

Correlational Research

Correlational studies involve measuring two or more variables. For that reason, this research is inherently quantitative. The researchers can then look at how related to variables are to one another. If two variables are related, or correlated, then we can use one variable to predict the value of another variable. The greater the correlation, the greater accuracy our prediction will have. For example, correlational research might be able to tell us what factors at home are related to greater student learning in the classroom. These factors might include things like eating a healthy breakfast, getting enough sleep, having access to a lot of books, feeling safe, etc. 

I often have my students think about car insurance to explain correlational research. Car insurance companies measure a lot of different variables, and then try to do their best to predict which customers are likely to cost them the most money (e.g., cause a car accident, have their car damaged, etc.). They know that on average younger males are more likely to cost them money, and that drivers who have received speeding tickets are more likely to cost them money. They also know that people living in certain areas are more likely to get into car accidents due to dense populations, or to have their car damaged while parked. Does this mean that a 16-year old boy who got a speeding ticket and lives in the city is definitely going to cause a car accident? No, of course not. Does this mean that getting a speeding ticket specifically causes later car accidents? No. It just means that the car insurance company knows that this type of person is more likely to cause the car accident, for any number of reasons, and uses this information to determine premiums. 

Correlational research can help us understand the complex relationships between a lot of different variables. If we measure these variables in realistic settings, then we can learn more about how the world really works. This type of research allows us to make predictions, and can tell us if two variables are not related, and thus searching for a cause-effect relationship between the two is a huge waste of time.

Correlation is not the same as causation! Even if two variables are related to one another, that does not mean we can say for certain how the cause and effect relationship works. Take caffeine average consumption and average test. Lets say we find that the two are correlated, where increased caffeine is related to higher test performance. We cannot say that caffeine caused greater test performance, or that greater test performance caused greater caffeine consumption. In reality, either of those could work! For example, students may drink more caffeine and this might lead them to perform better on tests. Or, the students who perform better on tests are then more likely to drink more caffeine. A third variable could be related to both of these as well! It could be that students who are more concerned about their grades might study more and achieve better test performance, and might also drink more caffeine to help them stay awake to study! We just don't know from the correlation alone, but knowing that the two variables are in some way related can be very useful information.

True Experiments

True experiments involve manipulating (or changing) one variable and then measuring another. There are a few things that are required in order for research to be considered a true experiment. First, we need to randomly assign students to different groups. This random assignment helps create equivalent groups from the beginning. Second, we need to change something (for example, the type of learning strategy) across the two groups, holding everything else as constant as possible. The key here is to make sure to isolate the thing we are changing, so that it is the only difference between the groups. We also need to make sure at least one of the groups serves as a control group, or a group that serves as a comparison. We need to make sure that the only thing being systematically changed is our manipulation. (Note, sometimes we can systematically manipulate multiple things at once, but these are more complicated designs.) Finally, we then measure learning across the different groups. If we find that our manipulation led to greater learning compared to the control group, and we made sure to conduct the experiment properly with random assignment and appropriate controls, then we can say that our manipulation caused learning. Taking the example from the correlational section, if we want to know whether drinking coffee increases test performance, then we need to randomly assign some students drink coffee and other students to drink a non-caffeinated beverage (the control) and then measure test performance. And then, we repeat to be more confident in our conclusions! Usually, we're repeating experiments with little changes to continue obtaining new information.

Experiments can also be conducted in a “within-subjects” design. This means that each individual participating in the experiment is serving as their own control. In these experiments, each person participates in all of the conditions. To make sure that the order of conditions or materials are not affecting the results, the researcher randomizes the order of conditions and materials in a process called counterbalancing. The researcher then randomly assigns different participants to different versions of the experiment, with the conditions coming up in different orders. There are a number of ways to implement counterbalancing to maintain control in an experiment so that researchers can identify cause and effect relationships. The specifics of how to do this are not important for our purposes here. The important thing to note is that, even when participants are in within-subjects experiments and are participating in multiple learning conditions, in order to determine cause and effect we still need to maintain control and rule out alternate explanations for any findings (e.g., order or material effects).

This type of experiment allows us to determine cause and effect relationships! True experiments are often be designed based on descriptive research or correlational research to determine underlying causes. If we really want to know how to promote student learning in the classroom or at home, then we need to know what causes learning.

Of course, true experiments are not without weaknesses. True experiments require a lot of control so that we can isolate the variables that are causing changes to occur. The more control we have, the better measurement we have. However, at the same time, the more control we have, the more artificial the experiment becomes. Just because we that a learning strategy causes learning in one specific experiment, doesn't mean that it will work the same way with different types of students, or in live classroom settings. In other words, the effect might not be generalizable. The solution to this problem is to approach the question with a number of different experiments, and to include the other research approaches to get a better picture of what is going on. One way we've tried to do this in research about learning is to utilize the lab to classroom model.

Lab to Classroom Model:

What is one solution to the big weakness associated with true experiments? Do a bunch more experiments! Not just any experiments, of course, but experiments that, together, help combat the weaknesses described above. When we talk about the lab to classroom model*, we are talking primarily about true experiments. In the lab to classroom model, we start out with basic, highly controlled experiments in very artificial settings. This allows us to best determine cause and effect relationships. We then slowly work our way up to the more realistic setting. We lose control when we do this, and it is more difficult to determine cause and effect, but when we take all of the experimental evidence together we can be much more confident in our conclusions!

The Lab to Classroom Model, image by Learning Scientists

* If you're not familiar with the lab to classroom model,  see this blog for a brief description, or listen to this podcast to hear Yana and I talk about the model.

BONUS -- A Design to Avoid: Pre-test Post-test designs

Finally, there is one design that you might see pop up here and there, and it has so many problems that it's worth mentioning explicitly. Pre-test post-test designs are exactly like what they sound like: you measure something before an intervention and after the intervention, and compare. This is not a true experiment, and does not allow us to determine cause and effect relationships.

For example, you might (unfortunately) see someone provide students with a pre-test to assess prior knowledge, then implement some sort of learning strategy, and then provide students with a post-test to see how much they have learned (compared to the pre-test). This design is extremely problematic! We truly have no idea whether the learning intervention caused any learning in this case. It could be that the students just got better over time, or that they learned from taking the pre-test, or that because they knew they were being tested before and after they were more likely to study at home! We cannot say the learning strategy did anything for certain. Using pre-tests and post-tests in research is acceptable, but only if there is a control group for comparison!

While not all methodologies discussed in this blog allow us to determine cause and effect, but they have other strengths that go along with them. This design does not allow us to infer causality, nor does it give us the in-depth, detailed information we get from descriptive research, nor does it tell us the relationships among many different variables!

Mar 11 Weekly Digest #100: Teachers' Implementations Of Learning Strategies

Mar 4 Weekly Digest #99: In Defense of Inquiry Learning

Markets for Diversifying Agriculture: Case Studies of the U.S Midwest

Agricultural diversification stands out as a critical strategy for addressing challenges and seizing opportunities within the agricultural landscape, especially in regions like the Midwest of the U.S. This research delves into the dynamics, opportunities, challenges, and key success drivers associated with agricultural diversification in the Midwest, focusing on three primary crops: oats, peas, and wheat. Employing a case study methodology grounded in empirical and contextual inquiry principles, the research aims to grasp the nuances of diversified agriculture. Data collection integrates primary and secondary sources, including semi-structured interviews and participation in field days. The data collection period spanned from October 2022 to February 2024. Interviews with 29 stakeholders, including farmers, industry representatives, agricultural cooperatives, and non-profits, provided insights into diversified agriculture practices.

Each case study provides in-depth insights into the opportunities, challenges, and key drivers of success associated with promoting diversified agriculture initiatives. These case studies underscore the significance of innovation, market access, sustainability, and collaboration in driving success within the industry. The cross-case analysis offers a comprehensive examination of the potential for agricultural diversification in the US Midwest. Through a comparative analysis of the three case studies, commonalities and key themes emerge, shedding light on stakeholder dynamics, business strategies, operational aspects, and scalability factors.

In summary, this research significantly contributes to the body of knowledge on agricultural diversification, offering insights that can guide future decisions, agricultural practices, and research endeavors aimed at promoting sustainability and resilience in the agricultural sector in the US Midwest.

Degree Type

• Master of Science
• Horticulture

Campus location

• West Lafayette

Advisor/Supervisor/Committee Chair

Additional committee member 2, additional committee member 3, usage metrics.

• Sustainable agricultural development
• Agricultural land planning

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Open Access

Peer-reviewed

Research Article

Influence of large open-pit mines on the construction and optimization of urban ecological networks: A case study of Fushun City, China

Roles Conceptualization, Project administration, Supervision, Validation

Affiliation College of Business Administration, Liaoning Technical University, Huludao, Liaoning, China

Roles Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Software, Validation, Visualization, Writing – original draft, Writing – review & editing

* E-mail: [email protected]

Roles Resources, Validation, Writing – review & editing

• Dongmei Feng, 
• Ge Bai, 

• Published: June 27, 2024
• https://doi.org/10.1371/journal.pone.0303016
• Peer Review
• Reader Comments

Under the long-term effect of mineral resource exploitation, especially open-pit mining, ecosystems are severely disturbed. Constructing and optimizing urban ecological networks influenced by open-pit mines based on mine–city coordination helps integrate ecological restoration and the construction of urban ecological environments. We applied an InVEST model to Fushun City to evaluate urban ecosystem services under the influence of large open-pit mines. Twenty-one key patches important for maintaining landscape connectivity were screened as the ecological sources in the network, from which ecological resistance surfaces were constructed by combining the impacts of mines on the environment. Minimum cumulative resistance (MCR) and gravity models were then used to extract and classify ecological corridors favorable to species migration and diffusion. Fushun City had large spatial differences in ecosystem service functions, with high-value areas concentrated in the forest-rich Dongzhou District and the northern Shuncheng District. Under the influence of open-pit mining, the ecosystem service capacity of the region south of the Hunhe River was poor and lacked ecological sources. Urban ecological resistance surfaces reached a maximum in the open-pit mining area, and 210 ecological corridors were estimated using the MCR model, of which 46 were important. Only two corridors crossed the West and East open pit, forming two “ecological fracture surfaces.” The Dongzhou and eastern Shuncheng districts had complex network structures and stable ecological environments. In contrast, the central and southern parts of Fushun City lacked ecological corridors owing to the influence of mining pits and gangue mountains, had simple network structures, and low connectivities with other sources. Combined with Fushun City’s development plan, we propose that ecological network optimization should add new ecological source sites, reconstruct and repair ecological corridors, and upgrade ecological breakpoints. This study provides reference and basis for ecological network research in mining cities influenced by open-pit mines.

Citation: Feng D, Bai G, Wang L (2024) Influence of large open-pit mines on the construction and optimization of urban ecological networks: A case study of Fushun City, China. PLoS ONE 19(6): e0303016. https://doi.org/10.1371/journal.pone.0303016

Editor: Marcela Pagano, Universidade Federal de Minas Gerais, BRAZIL

Received: November 16, 2023; Accepted: April 17, 2024; Published: June 27, 2024

Copyright: © 2024 Feng et al. This is an open access article distributed under the terms of the Creative Commons Attribution License , which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Data Availability: The data that support the findings of this study are openly available in public repository "Figshare" at https://doi.org/10.6084/m9.figshare.25390726.v1 .

Funding: This research was supported by the following grants:(1) Ministry of Science and Technology of the People's Republic of China (No. 2017YFC1503102). (2) The Educational Department of Liaoning Province (No. LJKR0141). (3) Liaoning Technical University (No. 55230010A032). The funders had no role in the study design, data collection and analysis, decision to publish, or manuscript preparation.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Although mineral resources have contributed notable to China’s economic and regional development, they have also harmed the ecological security of the region [ 1 , 2 ]. During mining, particularly open-pit mining, vegetation, topsoil, and rock removal occupy and destroy land resources, thereby rapidly aggravating the fragmentation degree of the mining landscape [ 3 – 5 ], reducing regional habitat patch areas [ 6 , 7 ], and destroying the integrity of the mining ecosystem’s health and its normal ecological processes [ 8 ], as well as negatively affecting the ecological processes of whole cities. Large pits, gangue hills, and geological disasters that occur during long-term open-pit coal mining have hindered or even blocked ecological flow and material circulation in cities [ 9 ], which leads to increasingly prominent ecological safety problems in cities [ 10 ].

Transforming and developing coal-resource-exhausted cities, as well as constructing ecological civilizations, have higher implications for protecting the ecological environment in mining cities. The ecological restoration of a mine can play a role in governing the mine structure, improving the soil quality, restoring vegetation, and restoring/rebuilding the ecosystem in the mining area [ 11 ]. However, after treating a single mining area, the focus should not only be on its internal landscape effect and ecological functions, but also the relationships between restoring the mine ecology and constructing and developing the ecological environment of mining cities to provide ecological security for such cities. The ecological network is a system that organically connects regional ecological resource patches and ecologically weak areas through linear spatial corridors [ 12 ] that allow broken ecological patches to connect and form a stable network structure. This structure has positive effects on optimizing landscape patterns and energy flow exchanges [ 13 ]. Thus, constructing and optimizing ecological networks are considered to be powerful measures for solving urban ecological environmental problems and ensuring ecological security [ 14 ].

Previous studies grounded in landscape ecology theory have investigated the ecological environment at various scales, thereby forming the fundamental research paradigm of ecological networks: ecological source–ecological resistance surfaces–ecological corridors [ 7 , 15 ]. To identify ecological source sites, previous studies have used the attributes of the patches themselves (e.g., nature reserves, large forested areas, and grasslands) [ 16 – 19 ] or have selected ecological indicators, such as ecosystem service capacity [ 20 , 21 ] and ecological sensitivity [ 22 , 23 ] or vulnerability [ 24 ]. However, these methods do not adequately consider the connectivity between the patches. Combining ecosystem services with landscape connectivity can improve source site selection [ 25 – 27 ]. To construct resistance surfaces, previous studies have considered natural conditions and the ecological environment (e.g., slope, elevation, vegetation cover, and land use patterns) [ 18 , 28 ]. In addition, some researchers have considered urbanization and human activity, both of which put stress on the ecological environment (e.g., population density[ 29 ] and the amount of nighttime light [ 6 , 30 ]), when modifying ecological resistance surfaces to increase the accuracies of the simulated spatial distributions of ecological corridors [ 31 ]. However, in the past, the hotspots of ecological network research mainly included urban areas [ 21 , 32 ], arid or semi-arid areas [ 33 , 34 ], agricultural and pastoral intertwined zones [ 17 , 35 ], and other areas with significant ecological characteristics. In contrast, few studies have been conducted on resource cities with a high degree of industrialization and a more serious ecological environment. Therefore, urban ecosystem development can be considered by superimposing the mine resistance surfaces [ 36 ]. The minimum cumulative resistance (MCR) model can estimate the energy consumption of species migrating between ecological sources and measure all possible species movement trends [ 27 ], which reflect the interactions among landscape patterns and ecological processes [ 37 ].Thus, the MCR model has been employed extensively to construct ecological corridors [ 38 , 39 ].

In this study, we applied the InVEST model to the Fushun urban area to evaluate the ecosystem service capacity and determine the ecological source areas using the landscape connectivity index. We then selected ecological corridor resistance factors from natural characteristics, ecological resources, and economic and social aspects. The factor weights were established using AHP to construct a comprehensive ecological resistance surface in Fushun City under the influence of open-pit mining. The MCR model was then used to extract the ecological corridors, which were classified using the gravity model. “Ecological breakpoints” were identified at sites where the ecological corridors crossed mines, expressways, and first-class highways. Combined with the planning of mining and mine rehabilitation in Fushun City, the ecological network optimization strategy proposed here for Fushun City was developed to provide a scientific basis for the reconstruction and optimization of the city’s ecological network. The method is universal and can be applied to other resource-oriented cities affected by large open-pit mines.

Starting from the characteristics of damaged urban ecosystems, this study quantitatively assesses the spatial differentiation characteristics of urban ecosystem service functions under the influence of large-scale open-pit mines, and incorporates the quantified ecosystem service functions into the identification and optimization of the ecological network, which is of great significance as a reference for the overall protection of regional ecosystem structure under the influence of large-scale open-pit mining and for the concrete solution of the problem of ecological environment damage.

Materials and methods

Fushun is known as the “Coal Capital” and is located in northeastern Liaoning Province, bordering Shenyang to the west (41°14´10"–42°28´32" N, 123°39´42"–125°28´58" E). Fushun is located in the middle temperate zone, has a temperate continental monsoon climate, and covers 11271.03 km 2 , with jurisdiction over four districts and three counties. The urban area is located on the alluvial plain of the Hun River and is surrounded by mountains on three sides. Fushun City has 34 kinds of mineral resources, including metals, non-metals, and coal, with a total of ~5.497 billion tons and total reserves of ~4.332 billion tons. After centuries of mining, the West open-pit mine has become the largest open-pit mine in Asia, which includes the West open-pit slope deformation area (7.03 km 2 ), coal mining subsidence area (18.41 km 2 ), and waste dumps (coal gangue and other waste accumulation; 21.49 km 2 ). Under the joint action of the East and West open-pit mines, coal mining influence areas were formed in the urban areas of the Xinfu, Wanghua, and Dongzhou districts of Fushun City ( Fig 1 ). In recent years, Fushun City has conducted vigorous mine management and ecological restoration and has used the comprehensive remediation and integrated utilization of the West open-pit mine as a breakthrough to propel the growth of the city. In this study, we constructed a potential ecological network for Fushun City, combined ecological restoration of the mining area with urban ecological network development, and proposed scientific recommendations for developing urban ecosystems in Fushun City.

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https://doi.org/10.1371/journal.pone.0303016.g001

Data sources

Remote sensing imagery of the Fushun urban area in 2022 acquired by the landsat 8 ( http://landsat.visibleearth.nasa.gov/ ) was used in this study, which has a resolution of 30 m × 30 m. Land cover data for the Fushun urban area in 2022 (30 m × 30 m resolution) were obtained by interpreting the remote sensing images. Digital elevation model data (30 m resolution) were obtained from the Geospatial Data Cloud ( https://www.gscloud.cn/ ), and normalized difference vegetation index data (30 m resolution) were obtained from the Google Earth Engine ( https://earthengine.google.com/ ). Nighttime light data were obtained from the National Oceanic and Atmospheric Administration website. Fushun Municipal Boundary [ 40 ] and road data (500 m resolution) were obtained from the Resource and Environment Science Data Center of the Chinese Academy of Sciences ( https://wwwresdc.cn/ ). Mining data were obtained from various mining companies, field surveys, and remote sensing imagery.

Rainfall data for 2022 were obtained from the 1 km resolution China monthly precipitation dataset for 1901–2022 published by the National Earth System Science Data Center ( https://www.geodata.cn/ ). Potential evapotranspiration data for 2022 were obtained from the 1 km resolution China monthly potential evapotranspiration dataset for 1901–2022 published by National Earth System Science Data Center ( https://www.geodata.cn/ ). Soil texture data were obtained from the SoilGrids dataset, which is a global soil dataset published by the International Soil Reference and Information Center ( https://files.isric.org/soilgrids/former/2017-03-10/data ). Soil depth data were obtained from the National Cryosphere Desert Data Center. ( http://www.ncdc.ac.cn/ ).

Research methods

Modeling urban ecosystem services influenced by open-pit mines..

Ecological sources are large habitat patches that play important roles in regional ecological processes and functions and are crucial for material circulation within regional ecosystems. Based on the habitat quality, sediment retention, water production, and carbon storage calculations, we set the weights of four types of ecosystem service functions. The correlations among the indicators were comprehensively considered when determining the weights, and the results of the four ecosystem service function indicators were normalized by range, divided into 3 km × 3 km grids, and averaged for each grid. The raster calculator in ArcGIS (ver. 10.8) was then used to investigate the ecosystem service functions in the region, which were classified into five levels (i.e., very important, important, average, not important, and very not important) using the natural breakpoint method. The principal components were calculated and the weights were determined using the principal component analysis method in the SPSS (ver. 27.0) software package [ 49 ]. Very important and important patches were selected as alternative patches. Using areas of 7, 4, and 1 km 2 as thresholds, alternative patches were categorized into super-large, large, medium, and small patches. Super-large patches were selected for landscape connectivity analysis, which was performed using the confer software package. Based on previous findings, the confer distance threshold was set to 2500 m and the patch connectivity probability was set to 0.5 [ 27 ].

Ecological resistance surface construction.

The ecological resistance surface refers to the factors in an ecosystem (e.g., topographic features, impacts of human activity, and land cover types) that produce resistance values to the flow of ecological substances among ecological sources [ 50 ]. Constructing comprehensive resistance surfaces can better reflect trends and potential ecological spatial processes [ 22 ]. Since Fushun is a coal-resource-exhausted city, the influence of mines on the ecological resistance surface cannot be ignored. We selected nine ecological resistance factors ( Table 1 ) from three dimensions: natural endowment, ecological resources, and economic society. Using the Yaahp software package, the relative weight of each resistance element was calculated by comparing its relative importance to other factors. The relative value of the resistance factor was set between 1 and 5. The raster calculator in ArcGIS was used to weight and sum each single-factor resistance surface to obtain a composite resistance surface.

https://doi.org/10.1371/journal.pone.0303016.t001

The different mining states of mineral resources have different degrees of resistance to biodiversity and biological migration near mines [ 51 ]. The cost of open-pit mining is lower than that of underground mining; however, the scale and amount of waste material generated by open-pit mining are both large, often occupying a large area of land resources. These conditions can lead to surface ecological environmental deterioration, which can increase the tendency for the land to become desertified. The impacts of mining, beneficiation, smelting, and tailing discharge at metal mines are much higher than those at coal and building material mines, and the ecological impacts of coal mining are larger than those of building material mining [ 52 , 53 ]. In this study, we referred to previous research [ 36 ] and constructed the mine resistance surface by investigating the mineral resources in the study area, analyzed the mining boundaries by combining remote sensing imagery with relevant historical mining data and consulting with mine ecological restoration experts, and assigned different ecological resistance values to the different mine types in the study area ( Table 2 ).

https://doi.org/10.1371/journal.pone.0303016.t002

Potential ecological corridor extraction.

Key ecological node identification.

Ecological nodes are nodes in the regional environment that are critical for the diffusion or migration of organisms. In general, an area with frequent human activity and high traffic flow in the ecological corridor is called an “ecological breakpoint” [ 55 ]. The presence of “ecological breakpoints” may lead to the isolation of originally intact habitats, which is unfavorable for biomigration or can threaten the survival of species, and should be emphasized in natural landscapes. In this study, we combined maps of the distributions of expressways, first-class highways, and mines to identify “ecological breakpoints.”

Ecological source selection

Using the InVEST model, the spatial distributions of the four types of ecosystem services in Fushun City (i.e., habitat quality, sediment retention, water yield, and carbon storage) were calculated ( Fig 2A–2D ). The spatial differentiation of habitat quality was obvious, and key areas were distributed in the water areas of Duofang Reservoir and the Hunhe River basin, as well as in the forested areas to the north and northeast of Fushun City. Forests can prevent surface soil erosion and are involved in water storage and precipitation. Therefore, high-value areas for sediment retention were located in woodland accumulation areas where the water yield was also higher. Unlike the other ecosystem services, the soil organic carbon content of cropland under anthropogenic activity was high.

https://doi.org/10.1371/journal.pone.0303016.g002

The lowest ecosystem service levels were located in urban construction lands and areas affected by large open-pit mines south of the Hunhe River. During open-pit mining, native surface vegetation and topsoil are stripped away. The open pit and waste accumulations near coal mines also cause the occasional spontaneous combustion of coal gangue, and the interiors of the mine pit and shechang (gangue mountains) completely lose their biological productivities, such that the biodiversity, soil and water conservation, and carbon storage levels are almost zero. The construction of roads and the residential land surrounding the mining area also occupied and destroyed some of the land resources; thus, the overall ecological environment of the open-pit mining impact area has seriously deteriorated. Fig 2 shows that after the recent ecological restoration of open-pit mines, the ecosystem services around the West open pit and restored areas of the east and west shechang have improved, except for the sediment retention capacity. Owing to the unstable geological conditions and steep terrain of the pits and sheds, as well as the long ecological restoration period for soil and water conservation, this effect requires 3–5 years to occur.

The principal component analysis indicated that the KMO value of the four ecosystem service functions was 0.604, and the weights for habitat quality, sediment retention, water yield, and carbon storage were 0.45, 0.24, 0.21, and 0.1, respectively ( Table 3 and Fig 2E ). Ecological patches were categorized into super-large, large, medium, and small patches, and the numbers and areas of the patches with different sizes were counted. The statistical results indicate that the super-large patches accounted for 51.3% of the total area, large patches accounted for 4.7%, medium patches accounted for 14.5%, and small patches accounted for 29.5%. The landscape fragmentation problem in Fushun City is therefore serious as a result of the influences of mining and human activity. Twenty-one ecological source sites were selected, mainly located in Dongzhou District and the northern Shuncheng District, with no ecological source sites in the impact area of large open-pit mines.

https://doi.org/10.1371/journal.pone.0303016.t003

Ecological resistance surface construction

ArcGIS was used to reclassify each resistance factor, assign grades and values, and weight and stack the values to obtain the base ecological resistance surface, mine resistance surface and integrated ecological resistance surfaces in Fushun City (Figs 3 – 5 ).

https://doi.org/10.1371/journal.pone.0303016.g003

https://doi.org/10.1371/journal.pone.0303016.g004

https://doi.org/10.1371/journal.pone.0303016.g005

The ecological resistance surface in Fushun City was higher in the western, central, and southern parts of the region, and lower in the northern and northeastern parts. The resistance value reached a maximum in the East and West open-pit mines and the Shuncheng District building material mining area. Large-scale coal mining not only led to changes in the original land use type, but the deep excavation of the open-pit mines and the high accumulation of coal gangue also produced mining area topography with large undulations, steep terrain, frequent geological disasters, and highly sensitive habitats. In addition, as coal resources and waste must be transported outward, the internal road network in the mining area was relatively rich, which seriously affects the flow of species. Abandoned open-pit mines undergoing ecological management and restoration, resource integration, and reuse are crucial for the ecological development of the city. The resistance value of the urban construction area was only lower than those of mines without ecological restoration, which can be attributed to a larger impervious surface area that hinders ecological processes, such as species migration and material circulation [ 56 ]. The low resistance value areas were mainly located in the northern Shuncheng District and the northern and southeastern Dongzhou District, which were less affected by human socioeconomic impacts and had superior natural endowments and rich ecological resources.

Potential ecological corridor extraction

Based on the ecological sources and comprehensive ecological resistance surface, the cost rasters between the ecological sources and destinations were calculated, and the minimum cumulative resistance channel between each source was obtained, which identified 210 ecological corridors. The interaction matrix between the source areas obtained from the gravity model was used, and the mean value of the interaction size (48.24) was set as the threshold value for classifying the ecological corridors. Ecological corridors with interaction sizes greater than the mean value were considered to be important ecological corridors (46), whereas those with values smaller than the mean were considered general ecological corridors ( Fig 6 ). Redundant ecological corridors that passed through the same source area were eliminated.

https://doi.org/10.1371/journal.pone.0303016.g006

The interaction matrix ( Table 4 ) indicates that the interaction intensities between ecological source sites No. 7 and No. 19, and between No. 7 and No. 5 were the highest (both >700), followed by the interaction intensity between sites No. 12 and No. 26 (523.95). The geographical space between ecological source sites Nos. 1 and 6 was very close; site No. 6 is rich in forest resources, and site No. 1 is mainly the Dahuofang Reservoir, which is dominated by watersheds. The interaction intensities among site Nos. 9 and 10, 11, 13, and 14 were greater than 10, but were separated from those of Nos. 3, 5, 7, 18, 19, and 21 by large open-pit mines and the main urban area; thus, their interaction intensities were very small (all <10). The lack of ecological sources and the high resistance values in the open-pit mines and the surrounding area caused the number of ecological corridors to be extremely low, and only two general ecological corridors passed through the open-pit mining area.

https://doi.org/10.1371/journal.pone.0303016.t004

Key ecological node identification

Based on the constructed ecological corridors, we identified “ecological breakpoints” by combining the expressway, first-class highway, and mine distribution maps. The Middle-Liaoning Ring and Shenyang–Jilin expressways pass through many important ecological corridors, and a first-class highway passes through the city center, intersecting with many general ecological corridors and with many important ecological corridors in the Dongzhou District, forming a total of 37 “ecological breakpoints.” Fig 7 shows that the ecological corridor between site Nos. 9 and 21 passes through the West open-pit mine, and the ecological corridors from site No. 9 to Nos. 3 and 19 passes through the western part of the East open-pit mine, thereby forming two “ecological fracture surfaces.”

https://doi.org/10.1371/journal.pone.0303016.g007

Ecological network optimization

The central and southern parts of Fushun City lacked ecological sources and had few ecological corridors. Considering the tight land resources in the city center and the wasted land resources influenced by the large-scale open-pit mines, we added ecological sources in the peripheral areas of the city center with high ecosystem service functions. The degree of fragmentation of cultivated land and the landscape near site No. 21 in the northern Shuncheng District was high. Integrating these small land patches can improve the degree of cropland fragmentation and create a new ecological source. Continued ecological management in the Xishechang District that connect it with the surrounding grasslands and plant grass with trees will allow the Wanghua District to form another ecological source. In addition, ecological restoration work is ongoing at the West open-pit mine. If the West open-pit mine is transformed into a large ecological park or a water storage power generation project, it can also become a new ecological source.

Woodlands are suitable for species exchange and diffusion and can better protect species diversity and provide temporary habitats for species movement as corridors. By connecting landscapes, woodlands also have a certain ecological protection function. The study area can directly use existing forested land to upgrade the general ecological corridors. In the central urban area, various green belts and boulevards will be constructed to restore and upgrade ecological corridors, thereby promoting the integrity of the urban ecological network.

The superimposition of ecological corridors and road networks produced 37 “ecological breakpoints,” 18 of which were located in important corridors, indicating that important ecological corridors were seriously divided by the road network and hindered the migration and diffusion of species. The breakpoints should be restored and reconstructed, warning signs and speed limits should be established, or special biological migration corridors should be constructed to mitigate these issues. The ecological corridors and mines were superimposed to extract two “ecological fracture surfaces.” Although the West open-pit mine is undergoing ecological management and restoration work, owing to the large area and depth of the mining pit, the re-greening project will require a longer period of time for completion. Currently, the southern, western, and northern sides of the West open–pit mine have achieved remarkable results, and biological migration can use the re-greened locations as corridors. Compared with the West open-pit mine, the East open-pit mining area is smaller, shallower, and was mined for a shorter period of time. The current implementation of mining and governance, owing to the expansion of the East open-pit mining work, will move the coal city road to the southern reconstruction. During this process, the ecological corridor to the west of the East open-pit mine will be affected. Therefore, the relationship between ecological environmental protection and mine development and utilization should be properly assessed before beginning the reconstruction and expansion project, and the construction of green mines should be achieved to reduce any damage to ecological corridors or provide alternative solutions.

Strengthening mine ecological restoration

The construction and optimization of urban ecological networks can improve urban ecosystem protection and promote sustainable urban development. However, the ecosystems in mining cities are fragile, and large-scale open-pit mining of mineral resources has harmed the natural environment further [ 57 ]. A series of geological disasters and environmental problems, including mined-out area breakdowns, surface cracks, landslides, and massive accumulations of coal gangue, have occurred successively. Since they are affected by multiple factors, the construction of ecological networks in mining cities is therefore more difficult than those in other cities.

Strengthening the ecological restoration of open-pit mines is necessary for city development, using the principle of “who mines, who manages, while mining, while managing.” With respect to unmanaged open-pit mines, in accordance with the principle of “who manages, who benefits,” geological disasters, land damage, vegetation destruction, and other ecological problems can be repaired through manual interventions to stabilize the geological environment, reclaim the damaged land, restore and improve the ecosystem functions [ 58 – 60 ], and motivate reconstruction and optimization of the ecological networks in mining cities.

Strengths and limitations

The InVEST model is a widely used tool in spatial planning [ 61 ], biodiversity conservation [ 62 ], ecological compensation [ 63 ], and other environmental management decisions [ 64 ] at various scales. Ecological sources are important patches that ensure regional ecological security. The InVEST model based on GIS is based on spatial data to quantify multiple ecosystem service functions in the study area and express them in the form of maps, which can realize the spatialization and dynamization of quantitative assessments of ecosystem service functions [ 65 ] and increase the scientificity of the source site selection from the perspective of the importance and integrity of ecological patch functions. In the study of ecosystem service functions of mining cities, it can visualize the difference in ecosystem service functions between restored and unrecovered areas of large-scale open-pit mines. The results of this paper are consistent with previous studies that have indicated that mining leads to rapid ecological environmental decline at mines; however, anthropogenic disturbances during the restoration of the mine ecological environment can improve and accelerate recovery [ 36 ].

This paper adopts the research paradigm of “ecological source-ecological resistance face-ecological corridor” to study the construction and optimization of urban ecological network under the influence of large open-pit mines, but there are still some limitations, which will be discussed and prospected below.

In the construction of resistance surface, this study selects 9 resistance factors from natural talent, ecological resources, and human development to construct a comprehensive resistance surface in Fushun city. However, the actual study of large open-pit mines is complex and the impact of mining activities on the surrounding ecological environment is also very complex. Moreover, resistance factor selection should be comprehensive and representative; however, how to more rigorously select factors scientifically to reflect the special characteristics of large open-pit mining areas and accurately simulate the ecological network of mining cities require further in-depth study.

As for the extraction results of ecological corridors, this study simplified the corridors into linear elements, and the width of ecological corridors obtained directly by using the MCR model was the pixel width of 30 meters in the grid data, which could not meet the needs of species migration. In fact, the different widths of corridors may have an impact on the ecological mobility, and the degree of connectivity of the network and the heterogeneity of the landscape in reality may also lead to changes in the shape and width of corridors [ 66 ]. Therefore, in the next step of the research work, we can consider refining and analyzing the identification of corridor width according to the actual situation of the study area and the results of previous research [ 67 ], so as to increase the consideration of corridor restoration.

This study mainly analyzes and discusses the single-year ecological flow of mining cities under the influence of large open-pit mines, and there is not enough research on temporal dynamics. Mineral mining in mining cities often lasts for more than a few decades, and the large open-pit mines in this paper have been mined for a hundred years, but this study has not studied the dynamic changes and dynamic relationships between ecological damage and ecological restoration areas in mining cities. Currently, under the promotion of the management policy of mining ecological environment protection and restoration, new trends of ecological conditions will also occur in large open-pit mines. In the subsequent research, the dynamic simulation and scenario assumptions of the ecological process in the study area can be constructed through the construction of a model to carry out the analysis of the temporal and spatial evolution of ecological flow, with a view to measuring the relationship between ecological environment destruction and restoration triggered by mining exploitation and clarifying the best path for ecological restoration.

Conclusions

Fushun City exists in China’s large open-pit mine-concentrated area. Under the joint action of urban construction and mining, the Fushun City’s ecological environment has suffered serious damages and become increasingly sensitive. Therefore, the construction of a complete ecological network planning system to restore the ecological balance of Fushun City is of practical significance. This paper utilizes the InVEST model to assess the ecosystem service function of Fushun City under the influence of large open-pit mines and determines the ecological sources by combining with the landscape connectivity index. Then it constructs a comprehensive ecological resistance surface in Fushun City, extracts ecological corridors in Fushun City using the MCR model, and finally determines ecological breakpoints by combining the distribution characteristics of the mines and the road network, so as to proffer suggestions for the optimization of ecological network management in the Fushun city area.

The results show that, first, critical ecosystem service areas influenced by large open-pit mines in Fushun City are located in the Dongzhou and northern Shuncheng districts, whereas low-value areas are located in construction lands at the city center and the areas affected by open-pit mining south of the Hunhe River. Second, based on a combination of ecosystem service functions and landscape connectivity, 21 ecological sources were identified. Under the influence of large open pit mining, the ecological sources in the study area were unevenly distributed, the internal connectivity of the landscape was weak, and the fragmentation degree was high. Third, the ecological resistance surface in Fushun City generally shows the distribution characteristics of high in the center and west, and low in the surrounding area. High ecological resistance value areas in Fushun City overlapped with mines and expressways. Fourth, the MCR and gravity models identified 210 corridors, including 46 important ecological corridors. The Dongzhou district contained a large number of important ecological corridors, the ecological network structure was complex, and the connectivities between source areas were strong. Few corridors were identified in the mining area, resulting in poor connectivity between the southern and northern parts of Fushun City. Finally, two “ecological fracture surfaces” were extracted under the influences of the west and east open-pit mines. Thirty-seven “ecological breakpoints” were extracted under the influence of the expressway and first-class highway network, 18 of which were located in important ecological corridors.

Based on the findings, Fushun City should strengthen its source protection, strengthen its broken landscape restoration and open-pit mine ecological environmental management/restoration practices, add new ecological sources and corridors, improve the general ecological corridors, and restore and renovate “ecological breakpoints” and “ecological fracture surfaces” in the region. Enhancing the living environment of the city center and ecological restoration at the mines south of the Hunhe River will improve the network stability and build a safer and more stable ecological network.

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• Published: 26 June 2024

Storing CO 2 while strengthening concrete by carbonating its cement in suspension

• Xiaoxu Fu 1 ,
• Alexandre Guerini 2 ,
• Davide Zampini 3 &
• Alessandro F. Rotta Loria   ORCID: orcid.org/0000-0001-6584-7526 1  

Communications Materials volume  5 , Article number:  109 ( 2024 ) Cite this article

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• Civil engineering
• Environmental impact
• Geochemistry

Cement is a key constituent of concrete and offers a large sequestration potential of carbon dioxide (CO 2 ). However, current concrete carbonation approaches are hindered by low CO 2 capture efficiency and high energy consumption, often resulting in weakened concrete. Here, we conceptually develop and experimentally explore a carbonation approach that resorts to injecting CO 2 into a cement suspension subsequently used to manufacture concrete, turning the carbonation reaction into an aqueous ionic reaction with a very fast kinetics compared to traditional diffusion-controlled approaches. This approach achieves a CO 2 sequestration efficiency of up to 45% and maintains an uncompromised concrete strength. The study shows that the CO 2 injection rate influences the polymorph selectivity of mineralized calcium carbonate (CaCO 3 ) depending on the local environmental conditions and impacts the strength of concrete. The technological simplicity of the proposed approach enables a reduced carbon footprint and promising prospects for industrial implementation.

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Introduction.

According to the Intergovernmental Panel on Climate Change, global greenhouse gas emissions continue to rise and have reached a net anthropogenic value of 59 ± 6.6 Gt CO 2 -eq in 2019 1 . The energy sector accounts for over 60% of such emissions, leaving nearly 40% of global emissions to other industry sectors 2 , 3 . The cement and concrete industries play a significant role in this context, with ordinary Portland cement production alone being the largest emitter and the source of ~8% of the global anthropogenic CO 2 emissions 4 . Meanwhile, ordinary Portland cement has a high potential for CO 2 sequestration owing to its inherent alkalinity, promising to turn the cement and concrete industries into carbon sinks via the conversion of CO 2 into solid crystals mainly consisting of calcium carbonate (CaCO 3 ). Stable carbonate crystals have a longer lifetime than structures made of cement and concrete, thus representing an optimal means to store CO 2 in such structures 5 , 6 .

Over the past decades, various efforts have focused on the reduction of the CO 2 emissions deriving from the cement and concrete industries by working on the whole life cycle of these materials, from the extraction of the involved raw materials to their processing 7 , 8 , manufacturing 9 , 10 , use 11 , 12 , and end of life 13 , 14 , 15 , 16 . In this context, two main categories of approaches have been developed to store CO 2 in the cementitious materials that constitute concrete during the manufacturing of such a mixture: hardened and fresh concrete carbonation approaches. Hardened concrete carbonation approaches were introduced in the 1970s 17 , 18 and gained limited attention until recently but remain confined to laboratory studies due to technological limitations. Fresh concrete carbonation approaches were introduced more recently 19 , 20 , 21 but already benefit from commercial pilots due to technological advantages 19 , 22 .

Hardened carbonation approaches involve concrete preparation and mixing, concrete casting, concrete exposure to CO 2 gas, and concrete hydration 23 , 24 , 25 . The pressure, temperature, duration, and general environmental conditions at which CO 2 is placed in contact with hardened concrete distinguish the different types of hardened concrete carbonation approaches. Besides these differences, all hardened concrete carbonation approaches involve chemical reactions that engage the active cementitious constituents of hardened concrete with the conversion of CO 2 gas into solid CaCO 3 crystal forms. Nevertheless, as these approaches are driven by diffusion-controlled kinetics, they are limited by the minimal extent of CO 2 diffusion in hardened concrete, which enables carbonation reactions from the surface of hardened concrete to a depth of a few millimeters 26 . Pressurized vessels, usually between 1 and 5 atm 27 , can improve the carbonation degree and penetration depth 24 , 28 , 29 . However, the resulting cost-effectiveness diminishes as the applied pressure increases 30 , with CO 2 uptake rates that remain within 5–20% 24 at the expense of significant energy and infrastructure needs. Furthermore, the nature of these approaches limits their applicability to precast concrete, as they require CO 2 -rich or high-pressure environments 31 .

Fresh concrete carbonation approaches involve concrete preparation and mixing with the simultaneous injection of CO 2 gas, concrete casting, and concrete hydration 20 , 32 , 33 . With these approaches, chemical reactions engage fresh concrete with the conversion of CO 2 gas into solid CaCO 3 crystal forms. Therefore, two main advantages characterize fresh compared to hardened carbonation approaches: (1) the possibility to carbonate a greater volume of concrete via CO 2 injections during mixing; (2) the possibility to incorporate relatively easily CO 2 injection nozzles in industrial processes.

Considering the advantages of fresh compared to hardened concrete carbonation approaches, increasing experimental investigations have been performed in recent years to maximize their performance 19 , 20 , 21 , 32 , 33 , 34 , 35 , 36 . However, the understanding of the reactions, kinetics, and mechanisms involved in fresh concrete carbonation approaches remains elusive, leading to limited CO 2 capture efficiencies 20 . This evidence, together with the fact that energy consumption induced by CO 2 pumping, purification, transport, and high-pressure vessels can involve greater emissions of CO 2 gas compared to those that are sequestered 5 , involves that the carbon capture potential of fresh concrete carbonation approaches remains largely untapped.

Motivated by the opportunity to improve the fundamental understanding and efficacy of fresh concrete carbonation approaches, this work presents an experimental laboratory study in support of an approach to carbonate fresh concrete that harnesses a key methodological difference compared to the state-of-the-art. The difference between the proposed approach and state-of-the-art approaches is that CO 2 gas is injected into a diluted cement suspension instead of fresh concrete, which completely changes the carbonation reaction kinetics. Specifically, the proposed approach resorts to a multi-stage concrete preparation method whereby CO 2 gas is first injected into a cement suspension, the resulting material is then used to achieve a cement paste of desired properties, and concrete is finally obtained by adding and mixing aggregates. The results of laboratory experiments (see the “Methods” section) indicate that injecting CO 2 gas into a cement suspension, rather than the conventional method of injecting CO 2 into fresh concrete, significantly accelerates constituent reactions and CaCO 3 precipitation kinetics. Therefore, under specific treatment conditions that are precisely identified via the developed experiments, not only the properties of the carbonated concrete can remain unchanged, but the carbon footprint associated with the production of such material can be reduced compared to current standards. This discovery supports more efficient concrete carbonation approaches and advances the understanding of mineralization processes, which are widespread in materials science and engineering.

Figure  1 presents scanning electron microscopy (SEM) images to illustrate the impacts of CO 2 gas injections with different volumes (2000, 4000, and 8000 standard cubic centimeters, i.e., scc; corresponding to 3.9, 7.9, and 15.7 g of CO 2 ) on the morphology of cement particles constituting the concrete mix design selected for this work (see the “Methods” section for details). The results illustrate the features of cement particles deriving from (a) a cement suspension that did not undergo any CO 2 injection (i.e., an uncarbonated cement suspension); (b–d) a cement suspension that underwent a CO 2 injection (i.e., a carbonated cement suspension); (e) a cement suspension that did not undergo any CO 2 injection and was subsequently mixed with additional cement (i.e., an uncarbonated cement paste); and (f–h) a cement suspension that underwent the injection of CO 2 and was subsequently mixed with additional cement (i.e., a carbonated cement paste).

The cement suspension is made of 50 g of cement and 100 mL of deionized water (DI-H 2 O), involving a water-to-cement ratio of w/c = 2. The concrete is prepared from the suspension by first adding and mixing 50 g of virgin cement, achieving a cement paste with w/c = 1, and then adding another 100 g virgin cement (w/c = 0.5) and mixing of aggregates. See the “Methods” section for details. a Uncarbonated suspension. b Carbonated suspension with 2000 scc of CO 2 . c Carbonated suspension with 4000 scc of CO 2 . d Carbonated suspension with 8000 scc of CO 2 . e Uncarbonated paste. f Paste deriving from a carbonated suspension with 2000 scc of CO 2 . g Paste deriving from a carbonated suspension with 4000 scc of CO 2 . h Paste deriving from a carbonated suspension with 8000 scc of CO 2 . Red arrows: crystal structures.

By comparing Fig.  1a with Fig. 1b–d , it is possible to assess the influence of CO 2 injections on the morphology of the particles that constitute a cement suspension. By comparing Fig.  1e with Fig. 1f–h , it is possible to assess the influence of CO 2 injections on the morphology of the particles that constitute a cement paste deriving from a carbonated cement suspension. By comparing Fig.  1a–d with Fig. 1e–h , it is possible to assess the influence of adding cement to a given suspension, which may or may not be carbonated with CO 2 gas, to achieve a cement paste for use in concrete.

The uncarbonated cement suspension (Fig.  1a ) and paste (Fig.  1e ) show the typical morphology of cement hydration products, with irregular shapes, rough surfaces, and no visible crystals. The injection of CO 2 into a cement suspension and the addition of cement to such suspension influence the morphology and size of cement particles, respectively. As a result of the carbonation, crystals deposited on the surface of most cement particles become visible (Fig.  1b–d and f–h , respectively). Such crystals are uniformly found on the surface of cement particles derived from a cement suspension (Fig.  1b–d ), whereas they appear both on the surface and interlocked within the bulk of cement particles deriving from a cement suspension mixed with additional cement after carbonation (Fig.  1f–h ). Larger amounts of injected CO 2 gas yield the formation of a larger number of crystals (Fig.  1b–d and f–h ). The crystals found on cement particles that derive from cement suspensions always resemble needles for increasing volumes of injected CO 2 (i.e., Fig.  1b–d ). In contrast, the crystals found on cement particles that derive from cement pastes resulting from carbonated cement suspensions resemble needles for relatively limited volumes of injected CO 2 (i.e., for 2000 and 4000 scc, Fig.  1f, g ) but become flakes for larger volumes of CO 2 (i.e., for 8000 scc, Fig.  1h ). Larger and more polydisperse cement particles are obtained when cement is added to a suspension after its preparation, irrespective of whether such suspension does not undergo carbonation (Fig.  1a vs. Fig. 1 e ) or does undergo carbonation (Fig.  1b–d vs. Fig.  1f–h ). Cement particles that derive from carbonated cement suspensions have a size <10 µm (Fig.  1b–d ), whereas cement particles that derive from virtually equivalent carbonated cement suspensions and subsequently mixed with more cement have a size that can exceed 20 µm (Fig.  1f–h ). Energy dispersive spectroscopy (EDS) analyses (Supplementary Fig.  1 ) show that the observed crystals have the major elemental compositions of O (45.1–45.6%), Ca (33.0–34.3%), C (13.1–13.8%), Si (3.0–3.5%), and Fe (1.5–1.7%). Other detected elements including S, Al, and K have elemental weights <1%.

Figure  2 illustrates the results of (a) thermogravimetric analyses (TGA), (b) differential thermal analyses (DTA), and (c) X-ray diffraction (XRD) spectra obtained for both carbonated and uncarbonated cement suspensions. The TGA curves reveal two distinct temperature ranges characterized by significant weight losses (Fig.  2a ). The first range is approximately located between 380 and 440 °C, whereas the second is between 520 and 740 °C. The first range corresponds to a dehydration range associated with the loss of absorbed water in the range of 105 to 400 °C and the CH dehydration in the range of 400–500 °C 37 . The second range corresponds to the decarbonation process typically taking place between 530 and 900 °C 38 . The peaks in the DTA curves at the corresponding temperatures (Fig.  2b ) corroborate these results. Uncarbonated cement suspensions exhibit the highest dehydration peak and the lowest decarbonation peak. As the amount of injected CO 2 increases, the dehydration peak decreases while the decarbonation peak intensifies, with no visible dehydration peak being observed for 8000 scc of injected CO 2 . The decarbonation peaks shift to higher temperatures with an increasing amount of injected CO 2 . Meanwhile, the decarbonation peak temperatures for uncarbonated cement and carbonated cement with 2000, 4000, and 8000 scc of CO 2 are 656, 668, 678, and 702 °C, respectively. The XRD spectra (Fig.  2c ) substantiate the results discussed so far by indicating the presence of calcium carbonate in the form of calcite and aragonite in the carbonated cement, along with the typical constituents of cement represented by C3S, C2S, ettringite, C–S–H, and portlandite; additionally, these results enable to remark the lack of visible peaks of calcite and aragonite in the uncarbonated cement. Therefore, the observed crystals on the surfaces of carbonated cement particles (Fig.  1 ) are CaCO 3 and not cement hydration products. As the amount of injected CO 2 increases, the relative intensity of most of the peaks also increases, indicating an increase in the overall crystallization degree.

a TGA curves of cement suspensions. b DTA curves of cement suspensions. c XRD spectra of carbonated and uncarbonated cement suspensions.

Figure  3 illustrates key variables related to the efficacy of the proposed approach: (a) pH and temperature variations of the suspensions during their preparation and carbonation; carbon capture performance expressed as (b) CO 2 capture efficiency, (c) CO 2 capture mass, and (d) carbonation degree of the resulting concrete as a function of the CO 2 treatment duration; and influences on (e) absolute unconfined compressive strength of uncarbonated and carbonated concrete and (f) normalized strength of carbonated relative to uncarbonated concrete.

a Suspension pH ( n  = 3 independent experiments) and temperature at different stages of the preparation process (raw data reported in Supplementary Tables  1 and 2 ). b CO 2 capture efficiency with different CO 2 injection durations ( n  = 3 independent experiments; raw data reported in Supplementary Table  3 ). c Carbonation degree of carbonated cement with different CO 2 injection durations ( n  = 3 independent experiments; raw data reported in Supplementary Table  4 ). d CO 2 capture mass per unit volume of concrete with different CO 2 injection durations ( n  = 3 independent experiments; raw data reported in Supplementary Table  5 ). e Unconfined compressive strength of the concrete specimens as a function of the curing time and the volume of injected CO 2 ( n  = 10 independent experiments; raw data reported in Supplementary Table  6 ). f Normalized strength relative to the uncarbonated material (raw data reported in Supplementary Table  7 ). Error bars show standard deviations.

The preparation of the cement suspension starts with the use of DI-H 2 O only, which has a pH of 7 at an ambient room temperature of 21.2 °C (Fig.  3a ). Next, DI-H 2 O is saturated with CO 2 gas, yielding a pH of ~5.3 without any significant temperature change. Afterwards, cement is added to the CO 2 -saturated DI-H 2 O (with no concurrent CO 2 injection), leading to an increase in pH up to the value of 12.60 ± 0.05 and a surge in the solution temperature from 21.2 to 23.1 °C under stabilized conditions. Finally, CO 2 is injected in the cement suspension for a time of up to 40 min, leading to an instantaneous decrease in pH from 12.60 ± 0.05 to 12.18 ± 0.08 during the considered time, which increases up to the value of around 12.6 under stable conditions (see the “Methods” section). After 40 min of carbonation, the stable and instant pH values are 12.18 and 12.63, corresponding to OH − concentrations of 0.015 and 0.043 M, respectively. Temperature drastically increases at the beginning of the CO 2 injection, but such an increase becomes less pronounced as carbonation progresses, stabilizing around 39.5 °C after 30 min.

The CO 2 capture efficiency decreases for longer injection durations, from 45.4% for a 10-min injection (2000 scc) to 26.2% for a 40-min injection (8000 scc) (Fig.  3b ). Despite this decrease, the carbonation degree increases with the amount of injected CO 2 (Fig. 3c ), starting from 3.3% when cement suspensions are uncarbonated and placed in contact with CO 2 from ambient air and achieving 17.2% for a CO 2 injection lasting 40 min. The absolute mass of captured CO 2 also increases with a higher amount of injected CO 2 (Fig. 3d ). Specifically, 5.2, 7.7, and 12.0 kg of CO 2 per unit volume of concrete are captured during 10, 20, and 40 min of injection, respectively.

Figure  3e, f shows the unconfined compressive strength of concrete specimens obtained from uncarbonated and carbonated cement suspensions after 3, 7, 28, and 56 days of curing. The strength shows a typical increase with the curing time due to ageing, irrespective of whether the concrete derives from cement suspensions that underwent carbonation or not (Fig.  3e ). Meanwhile, reference to the average strength of the prepared concrete specimens allows us to identify several noteworthy trends. Although the average strength of carbonated concrete is always higher than the strength of uncarbonated concrete at early stages of curing (i.e., at 3 days), such strength can be higher or lower than the average strength of uncarbonated concrete at successive stages of curing (i.e., at 7, 28, and 56 days) depending on the amount of injected CO 2 (Fig.  3f ). Concrete deriving from cement suspensions free of carbonation displays average strengths of 22.9 ± 4.0, 31.0 ± 2.5, 35.4 ± 2.7, and 36.5 ± 4.8 MPa after 3, 7, 28, and 56 days, respectively. After 3 days of curing, the average strength of concrete deriving from cement suspensions that underwent carbonation is at least 10% higher than the average strength of uncarbonated concrete. After 7, 28, and 56 days, the average strength of concrete deriving from cement suspensions that underwent carbonation is generally smaller (down to 20.7%) than the average strength of uncarbonated concrete for 2000 scc and 4000 scc of injected CO 2 . In contrast, after 7, 28, and 56 days, the average strength of carbonated concrete is generally higher (up to 23.1%) than the strength of uncarbonated concrete for 8000 scc of injected CO 2 . Besides these considerations, an analysis of the standard deviation of these latter data suggests that the actual average strength of carbonated concrete may not be statistically higher than that of uncarbonated concrete. Meanwhile, it does indicate that the strength of carbonated concrete is at least not compromised compared to the strength of uncarbonated concrete for 8000 scc of injected CO 2 .

CaCO 3 precipitation and its impact on concrete strength

The strength of concrete strongly depends on the constituents and the chemical reactions characterizing such material. The proposed carbonation approach induces changes in the constituents and reactions that characterize concrete, which influence the structure and properties of such material.

In general, CaCO 3 precipitates in three main polymorphs: calcite, aragonite, and vaterite. Calcite is the stable polymorph and exhibits thermostability 39 , 40 . Aragonite is generally less stable than calcite and transitions to such polymorph at a relatively slow rate under ambient conditions 39 . Vaterite is unstable and hence uncommon in natural environments, transforming into aragonite and calcite at temperatures ranging from 0 to 30 °C and 60 to 80 °C, respectively 39 , 40 . CaCO 3 is recognized as calcite when it decomposes in TGA within the range 650–900 °C, whereas is considered as aragonite when it decomposes within the range 530–650 °C 38 . Meanwhile, weight losses in TGA between 500 and 700 °C are attributed to poorly crystalline CaCO 3 , whereas weight losses between 700 and 900 °C are attributed to highly crystalline CaCO 3 37 , 41 .

The results of this work indicate that carbonated cement suspensions subsequently used to manufacture concrete undergo the precipitation of CaCO 3 crystals that vary in quantity and morphology (Fig.  1 ). The quantity of CaCO 3 precipitations essentially depends on the amount of injected CO 2 and increases for larger volumes of injected CO 2 . The morphology of CaCO 3 precipitations depends on the crystal polymorph type and the crystallization degree (i.e., the ratio of crystalline to amorphous precipitated minerals). As TGA results support that decarbonation occurs between 530 and 900 °C (Fig.  2a ), the achieved CaCO 3 precipitations are a mixture of calcite and aragonite, as also substantiated by the XRD results (Fig.  2c ). The results also indicate a shift toward higher temperatures of the decomposition and decarbonation peaks for different CO 2 treatments (Fig.  2b ). Thus, changes in the polymorph type and crystallization degree take place.

The formation of a mixture of different CaCO 3 polymorphs can be attributed to two formation pathways of such compounds due to the hydration and carbonation of concrete. During the hydration and carbonation of concrete, which occur nearly simultaneously (although carbonation is faster than hydration 23 ), two main compounds contribute to the precipitation of CaCO 3 : calcium silicate hydrate (C–S–H) and calcium hydroxide (Ca(OH) 2 ). Another two compounds, represented by calcium aluminate (Ca 3 Al 2 O 6 ) and calcium aluminoferrite (Ca 4 Al 2 Fe 2 O 10 ), can also form as a result of CO 2 injections but typically in a significantly smaller fraction than calcium silicates. The reason is that calcium aluminate has a fast hydration reaction rate but remains rather inactive with CO 2 42 , and calcium aluminoferrite also shows limited reactivity with CO 2 43 . Since C 3 S and C 2 S are practically insoluble in water, the direct carbonation of them is rather slow.

The hydration reaction of calcium silicates (tricalcium silicate, C 3 S; dicalcium silicate, C 2 S) yields C–S–H and Ca(OH) 2 as follows:

In turn, Ca(OH) 2 reacts with CO 2 and forms CaCO 3 as follows:

In addition, C–S–H can also react with CO 2 and form CaCO 3 as follows:

CaCO 3 crystals formed via these two pathways yield different polymorphs: CaCO 3 formed from Ca(OH) 2 tends to be calcite, whereas CaCO 3 formed from C–S–H tends to be aragonite 38 , 44 . Available carbonation studies either take for granted that CaCO 3 precipitations are calcite or do not discuss the polymorph type. However, an analysis of these studies 20 suggests that CaCO 3 precipitations consist of a mixture of both calcite and aragonite even in these cases.

The changes in the polymorph type and crystallization degree can be attributed to temperature variations because these variables are strongly sensitive to temperature 40 . Following the formation of a calcite–aragonite mixture through pathways ( 3 ) and ( 4 )–( 6 ), a transition of aragonite to calcite characterizes any cement-based material exposed to CO 2 (e.g., naturally present in the air or artificially injected). In the proposed carbonation approach, the injection of CO 2 into a suspension involves intense exothermic reactions that enhance the temperature rise that would naturally occur due to cement hydration (Fig.  3 ). This enhanced temperature rise has two main effects. First, it accelerates the transition of aragonite into calcite, with a larger proportion of aragonite turned into calcite for a larger amount of injected CO 2 (at a given flow rate) because of more significant temperature variations (Fig.  3 ). Second, it increases the crystallization degree of precipitated CaCO 3 crystals. Both outcomes can be inferred from the shift of the decarbonation peak towards higher temperatures for a larger amount of injected CO 2 (Fig.  2b ).

CaCO 3 precipitations in freshly cast concrete are generally recognized to enhance the early-stage strength of such material through so-called accelerated curing 21 , 45 . This result partly derives from the formation of dense calcium carbonate layers in some of the material pores 46 and partly from the significant degree of cement reaction, either through carbonation or hydration, which is much higher than that achieved through typical steam curing regimes. The extra nucleation seeds provided by CaCO 3 precipitations are the main factor of such acceleration 21 . Meanwhile, having more cement constituents reacted, whether through carbonation or hydration, is also beneficial for early-stage strength development 47 . This evidence has been observed via fresh concrete carbonation 20 , 32 , 48 and hardened concrete carbonation 44 , 49 , 50 .

In contrast, CaCO 3 precipitations and/or crystal transitions at later stages are typically detrimental to the strength of concrete. This evidence results from the fact that aragonite typically has a higher density (2.94 g/cm 3 ) than calcite (2.71 g/cm 3 ) 51 , which implies that polymorph transitions inevitably induce changes in the volume and shape of these crystals in the concrete structure, leading to deleterious cracking 44 , 52 , 53 . For this reason, carbonation approaches are considered successful when they do not affect the strength of concrete due to the addition of CaCO 3 crystals. Accordingly, typical carbonation approaches show, at best, unchanged values of strength, especially after 28 days 23 .

By injecting CO 2 into a cement suspension during mixing, the carbonation approach proposed in this work provides three key opportunities:

It employs less energy compared to that required to carbonate fresh and hardened concrete, as CO 2 gas is injected into a liquid that has a viscosity comparable to water (i.e., significantly inferior to fresh concrete).

It allows harnessing the large surface area of cement particles floating in the water and engaging only a portion of fresh cement with reactions with CO 2 , as cement is added to a suspension after its carbonation to achieve a paste for use in concrete. While achieving CaCO 3 precipitations around some cement particles, this approach avoids the enclosure of most cement particles. This ability is favorable because cement particles encapsulated by CaCO 3 crystals cannot yield the formation of C–S–H and involve an aggregation of CaCO 3 -coated particles into clusters with interconnected and unwanted pores, ultimately leading to deteriorations in the strength of concrete 20 .

It fosters temperature variations during the CO 2 treatment of a cement suspension, resulting in the precipitation of more stable and crystalline CaCO 3 for larger temperature variations associated with larger amounts of injected CO 2 (at a given flow rate). This ability is favorable because stable CaCO 3 crystals remain unaffected by polymorph transitions during the subsequent concrete preparation with additional cement and aggregates, curing, and lifetime.

The obtained results specifically allow us to postulate that the variable strength achieved for variable amounts of injected CO 2 is due to a variable conversion of CO 2 into more stable and crystalline forms of CaCO 3 . In particular, when 2000 and 4000 scc of CO 2 are injected in a cement suspension, the proportion of CO 2 that is turned into stable and crystalline forms of CaCO 3 is limited and subsequently results in unwanted polymorph transitions and volume changes. In contrast, when 8000 scc of CO 2 is injected in a cement suspension, the proportion of CO 2 that is turned into stable and crystalline forms of CaCO 3 is more significant and subsequently involves minimal polymorph transitions. As a result, the strength of concrete remains uncompromised through the presence of durable and strong calcite deriving from the conversion of CO 2 into solid crystals (Fig.  1 ).

In order to substantiate the proposed mechanism behind the performance of this carbonation approach, experiments involving the injection of the same amount of CO 2 (i.e. 8000 scc) with different flow rates over different timeframes (i.e., the reference flow rate of 200 sccm over 40 min and the two additional flow rates of 100 and 400 sccm during 80 and 10 min, respectively) were designed and conducted (see the “Methods” section). The results are shown in Fig.  4 . The injection of higher CO 2 flow rates in cement suspensions results in faster temperature increases in such suspensions per unit time (Fig.  4a ). Maximum temperatures of 16.5, 20.4, and 22.2 °C are measured for flow rates of 100, 200, and 400 sccm after 70, 52, and 45 min, respectively. However, at the time the same volume of 8000 scc of CO 2 is injected in cement suspensions, temperatures of 16.2, 19.1, and 13.8 °C are recorded for 100, 200, and 400 sccm, respectively. Therefore, the highest temperature is achieved for the reference flow rate of 200 sccm. All carbonated specimens with a volume of 8000 scc of CO 2 exhibit a higher strength compared to the uncarbonated concrete, regardless of the applied flow rates or the curing time (Fig.  4b ). This evidence supports that there is a threshold value of injected CO 2 and interconnected amount of CaCO 3 crystals in concrete that overcomes the negative influence of possible polymorph transitions and yields a strength increase as opposed to a strength decrease compared to uncarbonated concrete. Meanwhile, the greatest strength characterizes the concrete deriving from a cement suspension carbonated with a flow rate of 200 sccm compared to 100 or 400 sccm at any curing time, supporting that there is a threshold temperature value for which CaCO 3 crystals mostly transition to more stable calcite instead of remaining aragonite compounds, or for which an increase in the crystallization degree is triggered. Accordingly, the concrete deriving from a cement suspension carbonated with a flow rate of 200 sccm is the only one that presents both CaCO 3 needles and flakes on its constituting cement particles, whereas the concrete deriving from a cement suspension carbonated with a flow rate of 100 and 400 sccm only presents CaCO 3 needles (Fig.  4c–h ).

a Trends of temperature variations in the carbonated cement suspension for different CO 2 flow rates ( n  = 3 independent experiments; raw data reported in Supplementary Table  8 ; error bars show standard deviations). b Compressive strength of concrete deriving from a paste placed in contact with different CO 2 flow rates relative to the reference uncarbonated concrete (reference values are dashed; n  = 5 independent experiments; raw data reported in Supplementary Table  9 ; error bars show standard deviations); and SEM images of the CaCO 3 crystals formed on the cement particles deriving from a suspension subjected to c 100 sccm, d 200 sccm, and e 400 sccm, or a paste resulting from a suspension subjected to f 100 sccm, g 200 sccm, h 400 sccm.

Figure  5 summarizes the key stages involved in the strength development of concrete resulting from the proposed carbonation approach. The proposed approach allows to engineer the sequence of hydration and carbonation reactions and tailor them to specific quantities of cement.

a Injection of CO 2 into a cement suspension. b Growth of CaCO 3 crystals in such a suspension (inlets b 1 and b 2 show the growth and transition of CaCO 3 crystals in the cement suspension). c Addition of cement and aggregates to suspension (inlet c 1 shows the transition of CaCO 3 crystals in the cement paste). d Dominant hydration of cement in concrete. e Development of interparticle bonding within concrete. f Optional carbonation of hardened concrete.

The proposed approach starts with the mixing of a small portion of cement powder with water while CO 2 is injected in the system (Fig.  5a ). Carbonation and hydration reactions commence concurrently, but carbonation is faster than hydration at this stage.

As CO 2 injection continues, CaCO 3 precipitates in the cement suspension while temperature rises (Fig.  5b ). Depending on the local environmental conditions, CaCO 3 crystals undergo polymorph transitions and changes in polymerization degree, covering a wider number and surface of C 3 S/C 2 S particles as time progresses (Fig.  5b1, b2 ). The precipitation of CaCO 3 in a suspension involves that most polymorph transitions and volume changes of such crystals occur early, limiting the potential for cracking and deleterious effects on the structure, properties, and behavior of concrete during its curing and lifetime.

Following the CO 2 injection, the second portion of cement powder and aggregates are introduced (Fig.  5c ), previously precipitated CaCO 3 crystals can be characterized by morphology changes, and new CaCO 3 crystals can be formed because of the contact with atmospheric CO 2 (Fig.  5c1 ). At this stage, mixing is performed as in any classical approach to manufacturing concrete. Thereafter, the CaCO 3 crystals can act as nucleation seeds for subsequent hydration of C 3 S and C 2 S, accelerating the hydration process (Fig.  5d ) and contributing to the enhanced early-age strength of concrete.

As the curing process continues, the degree of hydration increases and C–S–H fills the concrete pores as in typical concrete curing (Fig.  5e ). This process is crucial to achieving interparticle bonding within the concrete matrix, ensuring strength development.

Finally, the concrete can optionally undergo an additional step of carbonation in its hardened state (Fig.  5f ), as in classical carbonation approaches of hardened concrete. In this context, carbonation can still characterize some quantity of cement and form a carbonated layer on the external surface of the concrete.

Carbon capture capacity, kinetics, and efficiency

Carbonation approaches should not only be evaluated in terms of their impacts on the structure and properties of carbonated materials, but also in terms of their ability to effectively store CO 2 in durable, solid crystal forms as a result of their CO 2 capture capacity, kinetics, and efficiency. The carbon capture capacity reflects the theoretical number of alkaline compounds that can react with CO 2 and form stable carbonates, representing the theoretical CO 2 sequestration potential of any carbonation approach. The CO 2 reaction kinetics determines the amount of CO 2 that can be captured for a given CO 2 injection duration. The CO 2 capture efficiency results from variable CO 2 sequestration capacities and reaction kinetics.

The main reactive alkaline compound in cementitious materials is Ca(OH) 2 , which comes from the hydration of C 3 S and C 2 S (Eqs. ( 1 ) and ( 2 )). This compound typically gives such materials a pH value between 12 and 13. In some instances, the pH can nonetheless exceed a value of 13 due to the presence of KOH or NaOH 54 . In this work, the pH of a well-stabilized cement suspension is 12.60 ± 0.05 (Fig.  3a ). This value closely aligns with the value of 12.33 that characterizes the pH of a saturated Ca(OH) 2 solution:

This result suggests that Ca(OH) 2 is the primary source of OH - in the considered suspension system. According to Eq. ( 3 ), Ca(OH) 2 reacts with CO 2 and forms insoluble CaCO 3 . However, according to Eq. ( 4 )–( 6 ), when Ca(OH) 2 is formed through Eqs. ( 1 ) and ( 2 ), C–S–H is concurrently formed in these reactions and can also react with CO 2 in conjunction with Ca(OH) 2 . Therefore, through a combination of Eqs. ( 1 )–( 6 ), the CO 2 -active component in cement is equivalent to CaO from a stoichiometric standpoint, allowing for the simplification of the previous equations to the following:

Thus, the carbon capture capacity can be calculated based on the CaO content in the materials.

To determine a more universal carbon capture capacity value for the proposed approach, a typical Type I cement composition is used as reference (Table  2 ). CaO constitutes 61.23% of the cement, resulting in ~30.6 g of CaO in the experimental setup employing 50 g of cement. In principle, according to Eq. ( 8 ), ~12,200 scc (24 g) of CO 2 can be captured and precipitated as CaCO 3 in the considered cement suspension if every molecule of CaO were to react with CO 2 . In practice, 2992 scc of CO 2 are captured when 8000 scc of CO 2 are injected into the cement suspension (Fig.  3 ). Therefore, the achieved CO 2 sequestration capacity is markedly smaller than the theoretical sequestration capacity of the carbonated cement suspension due to two reasons: (1) as CO 2 is injected, the surfaces of cement particles progressively become partly or entirely covered by CaCO 3 crystals (Fig.  1 ), and hence less reactive to CO 2 ; (2) as CO 2 is injected for a limited time, not all the CO 2 can react with the available cement particles.

The obtained results also indicate a decrease in the CO 2 reaction rate, which is attributed to a decrease in the OH - concentration in the material and a corresponding decrease in pH. An analysis of the reaction kinetics corroborates this evidence. Since a series of chemical and physical reactions develop during the proposed carbonation process, it is essential to know which one is the rate-control step. CaCO 3 precipitation relies on the concentrations of the two reactants, Ca 2+ and CO 3 2− , as indicated by the following equation:

The presence and concentration Ca 2+ and CO 3 2− in the aqueous suspension rely on their reaction routes.

On the one hand, the presence of CO 3 2− comes from CO 2 dissolution in an aqueous solution, which follows a series of chemical equilibria. First, CO 2 transitions from a gaseous to an aqueous environment:

As CO 2 comes in contact with H 2 O, the formation and ionization of carbonic acid take place, which supply H + and CO 3 2− according to the following:

As CO 2 injection occurs, the concentration of CO 2 (g) can be considered infinite (Eq. ( 11 )). The consumption rate of H + plays a crucial role in shifting the chemical equilibrium to the right and increasing the concentration of CO 3 2− (Eqs. ( 11 )–( 13 )). The following acid-base neutralization reaction is very fast:

Therefore, the dissolution of Ca(OH) 2 is the rate-determining step, according to the following:

As Eq. ( 15 ) is the main reaction that generates OH − in the system, the pH turns out to be the indicator of the overall reaction rate. During CO 2 injection, the pH decreases from 12.60 to 12.18, leading to a decrease in OH − concentration from 0.040 to 0.016 M and, hence, a concentration change of 0.024 M (Fig.  3 ). This OH − concentration change is larger than half of the initial OH − concentration. This decrease in OH − concentration affects the rate of CO 2 dissolution, which provides CO 3 2− . Notably, the temperature increase during the CO 2 injection also impacts the Ca(OH) 2 solubility (for Ca(OH) 2 , K sp (22 °C) ≈ 7.95 × 10 −5 ; K sp (40 °C) ≈ 5.4 × 10 −5 ). The OH − concentration under saturated conditions decreases from 0.043 to 0.038 M under such temperature increase and involves a concentration change of 0.005 M. However, the observed OH − concentration decrease is significantly larger than the OH − concentration drop caused by temperature. Therefore, the primary limitation to OH − concentration maintenance still comes from Ca(OH) 2 dissolution.

On the other hand, Ca 2+ comes directly from dissolution of Ca(OH) 2 . The reactions involved are as follows:

Equation ( 16 ) indicates the formation of Ca(OH) 2 . Equation ( 17 ) indicates the dissolution of Ca(OH) 2 . Equation ( 18 ) indicates the diffusion of ions from the particle surface to the bulk solution. Under unagitated conditions, the rate-controlling step is the diffusion step expressed in Eq. ( 18 ) 55 . However, in a vigorously agitated system like the one that characterizes the proposed approach to inject CO 2 into a cement suspension while it is mixed, diffusion is accelerated, and the rate-controlling step is the dissolution of Ca(OH) 2 at the surface instead 56 , as expressed in Eq. ( 17 ). Therefore, the decreased CO 2 capture rate is caused by a decrease in the OH - concentration in the material and a corresponding decrease in pH.

Most fresh concrete carbonation approaches have limited CO 2 capture efficiency of up to 10% 20 . The proposed carbonation approach achieves a CO 2 capture efficiency that surpasses 45% when injecting 2000 scc of CO 2 into the system and remains high at 26.2% when injecting a volume of 8000 scc CO 2 (Fig.  3 ). In this context, the following aspects are noteworthy: (1) the developed experiments are performed by using an uncapped beaker container, which does not prevent the dispersion of CO 2 into the atmosphere; (2) the experiments do not incorporate any looping system, which could further allow to enhance the treatment efficacy by lengthening the retention time of CO 2 in the suspension; (3) any upscaled application of such an approach would lengthen the retention time, enhancing CO 2 capture efficiency. Therefore, significant margins for improvement characterize upscaled implementations of the proposed carbonation approach, which is already more advantageous than state-of-the-art approaches. Emerging carbonation approaches involving the carbonation of wastewater are also being proposed for applications in concrete manufacturing and may be considered as a valuable pathway 57 , 58 . Notably, the approach proposed in this work could also carbonate appropriately treated wastewater instead of fresh water for the purpose of concrete manufacturing.

Carbon footprint

Carbon footprint is another key metric that can help determine the competitiveness of any CO 2 capture technology. Based on a Cradle-to-Gate Life Cycle Assessment (LCA), classical cement manufacturing has a global warming potential of 519 kg CO 2 -eq per functional unit, with 311.4 kg CO 2 -eq from fuel burning and 207.6 kg CO 2 -eq from limestone calcination. By assuming to carbonate the same functional unit of cement with the proposed approach for subsequent use in concrete, the global warming potential is reduced to 500.3 kg CO 2 -eq. In other words, the production of one ton of cement leads to a reduction of 18.7 kg CO 2 -eq in global warming potential. When applied to the entire global cement production, this amounts to a substantial reduction of 82.28 million tons of CO 2 emissions 59 , 60 . Put into perspective, this reduction is approximately equivalent to the annual CO 2 emissions of 18 million automobiles resorting to combustion 61 .

Promisingly, the developed LCA calculations unfavorably consider various aspects in the calculations, which would likely result in even more positive outcomes in the carbon footprint of industrial applications of the proposed technique. First, the carbon footprint calculations use a CO 2 capture efficiency of 26.2%. However, the actual CO 2 capture efficiency in upscaled applications of the proposed approach can be significantly higher due to the longer retention time of CO 2 in the mixer CO 2 . Second, CO 2 injection is considered a one-round procedure. However, the CO 2 injection in an upscaled process can be recursively applied or implemented with a looping system, increasing the CO 2 capture efficiency. Third, the proportion of carbonated cement for a functional unit is set at 1/4, which aligns with the laboratory conditions considered in this work. However, this proportion can be increased in an upscaled process, as long as the strength of the carbonated concrete is not compromised.

In summary, the innovative suspension-based concrete carbonation approach developed here not only demonstrates a reduced footprint but also exhibits potential for further scalability, rendering it an attractive candidate for industrial applications. This approach effectively addresses two prominent concerns within the domain of carbon capture through concrete carbonation. The first concern pertains to the potential weakening of concrete strength as a result of carbonation, necessitating additional cement usage to compensate for strength loss. This study reveals that by facilitating carbonate crystal depositions in the cement suspension phase, the proposed approach can, in fact, maintain an uncompromised strength. The second concern relates to the energy consumption associated with the carbonation treatment process, which encompasses CO 2 purification, pumping, transportation, and the use of high-pressure vessels. The cumulative effects of these processes could render the concrete carbonation approach carbon-positive 5 . However, the approach developed in this study minimizes energy consumption during CO 2 introduction through simplified and less rigorous procedures.

Conclusions

This work introduced an approach to trap CO 2 into fresh concrete by carbonating a portion of its cement in suspension. Laboratory experiments and LCA calculations support that the developed approach: (1) involves an active absorption of CO 2 during concrete manufacturing as opposed to conventional concrete production procedures; (2) benefits from a CO 2 capture efficiency of up to 45%; and (3) yields carbonated concrete with an uncompromised strength. The study provides a mechanistic analysis of the physico-chemical processes that characterize the proposed carbonation approach, which not only may underpin future enhancements of the proposed method but also inform the development of other approaches to carbonate fresh concrete and cementitious materials. By modifying classical concrete manufacturing processes only minimally, the proposed carbonation approach offers promise for industrialization. The possibility to enhance the treatment efficacy of the proposed approach in industrial scenarios, as described in this work, further supports its potential to decarbonize the cement and concrete industries.

The promise of the carbonation approach proposed in this work is assessed through four central sets of experiments:

Set 1 : The first set of experiments applies CO 2 injections to cement suspensions.

Set 2 : The second set of experiments imposes the same CO 2 injections on virtually equivalent cement suspensions, which are subsequently mixed with additional cement to achieve a cement paste of the desired water-to-cement ratio.

Set 3 : The third set of experiments imposes the same CO 2 injections to virtually equivalent cement suspensions, which are subsequently mixed with additional cement and aggregates to achieve a concrete mix design.

Set 4 : The fourth set of experiments imposes different CO 2 injection flow rates but reaches the same volume of injected CO 2 via different injection durations in cement suspensions.

Set 1 allows determining the chemical and physical properties of carbonated cement suspensions. Set 2 allows assessing the chemical and physical properties of cement pastes deriving from carbonated cement suspensions. Set 3 allows assessing the strength of concrete deriving from carbonated cement suspensions subsequently mixed with additional cement and aggregates. Set 4 allows to expand on the mechanistic understanding of the physico-chemical processes that characterize the proposed carbonation approach with specific reference to the role of temperature and amount of injected CO 2 on the results of the carbonation. Experiments without any CO 2 injection are also performed for reference.

Materials preparation

The materials addressed by experimental sets 1–3 are prepared by using a 150 mL beaker and following the steps detailed hereafter (Fig.  6 ). Initially, 100 mL of deionized water (DI-H 2 O) with a resistivity of 18.2 MΩ cm is introduced into the beaker. Next, CO 2 gas of high purity (99.9%) is introduced into the DI-H 2 O at a flow rate of 200 standard cubic centimeters per minute (sccm) for a duration of 20 min while stirring is continuously imposed. This process ensures the establishment of a CO 2 -saturated condition and maintains a consistent initial condition for each test. Meanwhile, experiments support that the absence of this step does not lead to different outcomes associated with the carbonation process of the cement suspensions. Subsequently, 50 g of Type 1 Portland cement (CEM I 42.5R) obtained from Vigier Cement Inc. is added to the CO 2 -saturated DI-H 2 O. Afterwards, CO 2 gas is injected into the prepared cement suspension for 10, 20, and 40 min. CO 2 injection flow rate is controlled by a mass flow controller (Alicat MC-300SCCM-D). The carbonated cement suspension achieved at this stage is the material addressed by experimental set 1, which, after preparation is moved to a Petri dish, dried in a CO 2 -free desiccator under 0% relative humidity and room temperature (~22 °C) for 24 h, and pulverization in an agate mortar for subsequent characterization.

(Step I) Initial condition; (Step II) CO 2 saturation; (Step III) Creation of cement suspension; (Step IV) Carbonation of cement suspension; (Step V) Creation of cement paste; (Step VI) Creation of concrete.

After the achievement of a carbonated cement suspension, experimental set 2 involves the addition of another 50 g of cement to achieve a fresh cement paste that is stirred for another 10 min. The cement paste achieved at this stage is the material addressed by experimental set 2, which is subjected to characterization following the same procedure employed for experimental set 1.

After the achievement of a cement paste deriving from a carbonated cement suspension, experimental set 3 involves the addition and mixing of cement and natural rounded crystal quartz sands and gravel sourced from Carlo Bernasconi AG Inc. to achieve a concrete mix design of a prescribed mass of constituents (Table  1 ). The resulting concrete achieved at this stage is the material addressed by experimental set 3, which is promptly molded into cylindrical specimens measuring 33 mm in diameter and 67 mm in height. A general-purpose lubricant (WD-40) is applied to the inner walls of the molds to facilitate the demolding process. The specimens are demolded following casting and a curing period of 24 h in a desiccator with a relative humidity of 100% and no CO 2 . Subsequently, they are subjected to curing in a dedicated room with a relative humidity of 100% for various durations: 3, 7, 28, and 56 days. Finally, the resulting concrete specimens are subjected to testing. Each experimental condition is analyzed based on the results of ten replicates.

Two sets of considerations are noteworthy with respect to the approach proposed here. On the one hand, although concrete preparation standards for laboratory use, such as ASTM C192 62 , do not specify a particular type of water, it is indeed recognized that tap water is more commonly utilized for concrete manufacturing as opposed to the deionized water employed for this work. Nevertheless, deionized water was chosen for this study to minimize variations in the properties (e.g., mineral content, pH, CO 2 saturation level) of the materials to be carbonated and hence achieve optimal control of the experimental conditions for the sake of this scientific investigation. In alignment with industrial approaches, the life cycle assessment conducted for this study indeed considered tap water, rather than deionized or distilled water, to provide representative results of real-world conditions.

On the other hand, although concrete mix designs with variable (e.g., lower) quantities of cement may be used in practice compared to those used for this work, such an aspect does not compromise the observed performance of the proposed approach to carbonate fresh concrete (see the “Results” section). In fact, only a minimal fraction of the total amount of cement that characterizes the concrete mix design chosen for this work is initially carbonated through the proposed approach. As this amount of cement is limited and lower than that considered in most concrete mix designs employed in practice, and its carbonation yields a carbon capture efficiency that remains superior compared to state-of-the-art approaches (even if not 100% efficient, as shown in the “Results” section and highlighted in the “Discussion” section), it is possible to consider the proposed approach, and especially its overarching methodological principle, as valuable alternatives compared to state-of-the-art methods.

Materials characterization

The characterization of the cement suspensions and cement pastes resorts to pH and temperature measurements, scanning electron microscopy (SEM), X-ray diffraction analyses (XRD), and thermogravimetric analyses (TGA). The characterization of the concrete resorts to unconfined compressive strength tests.

pH and temperature measurements resort to an Elite pocket tester by Thermo Scientific. They allow us to measure the considered variables during the preparation and possible carbonation of cement suspensions and pastes. The reported pH values during carbonation refer either to immediate measurements after a certain duration of CO 2 injection (“instant pH “ in Fig.  3a ) or to measurements collected for stabilized solutions after stirring them for 10 min to let excessive hydroxide donors (if present) to dissolve (“equalized pH” in Fig.  3a ).

SEM analyses use JEOL JSM-7900FLV equipment facilitated with energy-dispersive X-ray spectroscopy (EDS). They allow us to characterize the morphology of dried particles of cement and CaCO 3 crystals.

XRD analyses use an STOE-STADI-P powder diffractometer equipped with an asymmetrically curved Germanium monochromator (CuK α 1 radiation, λ  = 1.54056 Å) and 1D silicon strip detector (MYTHEN2 1K from DECTRIS). The line-focused Cu X-ray tube is operated at 40 kV and 40 mA. Intensity data from diffraction angles of 5°–70° (2 θ ) are collected for 45 min per sample. Phase identification is made by Rietveld refinements using the GSAS-II software for semi-quantitative analysis. Inorganic crystal structure database (ICSD) is used to obtain the standard spectra of crystals. Specifically, ICSD 15194, ICSD 15471, ICSD 18166, ICSD 79550, ICSD 87951, ICSD155395, and ICSD 162744 spectra are used, corresponding to aragonite, portlandite, calcite, belite, C–S–H, ettringite, and alite, respectively.

TGAs employ Netzsch’s simultaneous thermal analysis system and allow to quantify key features of CaCO 3 crystal precipitations from weight loss data, including decarbonation peaks, CO 2 capture rates, and carbonation degree. Approximately 20 mg of the powdered samples are subjected to TGA. The samples are heated from room temperature to 1000 °C at a heating rate of 10 °C/min under an inert N 2 atmosphere. The weight loss occurring between 500 and 900 °C is determined as the total loss of CO 2 resulting from the decomposition of carbonates. The CO 2 capture efficiencies are calculated as follows:

The carbonation degree is calculated as follows:

The theoretical CO 2 sequestration capacity is calculated via the composition of cement outlined in Table  2 . A typical composition of type I cement is utilized to calculate a based on the consideration of calculating a universal value of such an approach to provide a concept of capacity level. While Na 2 CO 3 and K 2 CO 3 both provide alkalinity, they do not have a significant effect on the CO 2 capture capacity calculation in this study because they are both highly soluble in water and CO 3 2− content in the suspension is thus not affected. The alkali content does influence the reaction kinetics, but the composition in Table  2 is solely used for capacity calculation.

Unconfined compressive strength tests are performed with a universal testing machine equipped with circular platens and a closed-loop hydraulic system manufactured by MTS Inc. These tests impose a displacement rate of 0.18 mm/min according to the ASTM C39 63 . The concrete specimens are initially capped using a sulfur-based capping compound (H-2959) obtained from Humboldt Mfg. Co. Capping is applied to achieve smooth bearing surfaces on both ends of the specimens and limit possible stress concentrations that would affect the results of the tests, thereby targeting the achievement of uniform loading conditions during the compression tests.

Carbon footprint analysis

The carbon footprint analysis developed as a part of this study is conducted based on an Environmental Product Declaration provided by CEMEX Polska Sp 64 . The Environmental Product Declaration adheres to standard EN 15804 65 and is verified by ISO 14025 66 . The primary analysis is conducted using a “Cradle-to-Gate” Life Cycle Assessment (LCA). The functional unit considered in the LCA is 1 ton of cement. The LCA process system boundary is shown in Fig.  7 . By following the same “Cradle-to-Gate” scenario as in the existing LCA, the carbon footprint of the developed suspension-based carbonation approach is evaluated within the scope of cement production, considering the additional CO 2 injection process required by such an approach. In this manner, the net reduction of global warming potential characterizing a standard cement production serving subsequent use for concrete production can be assessed.

Gray box: Cement production involved in the LCA calculation; Out of the gray box: the subsequent route of cement.

The following assumptions are made to perform the calculations:

40% of the total CO 2 emissions deriving from a cement plant is attributed to fuel combustion, whereas 60% is attributed to limestone calcination 67 .

Flue gas from a cement clinker calcination plant is used as the CO 2 source, with a CO 2 content of 21.76% (dry basis). CO 2 is regarded as the sole active constituent in the gas.

25% of the total employed cement in a given volume of concrete is considered to be carbonated with CO 2 in suspension (i.e., the same ratio applied in the laboratory test), whereas the remaining 75% is subsequently employed after treatment for concrete manufacturing.

Tap water instead of deionized water is used in the calculation for consistency with the classical concrete preparation scenario. Water consumption serving concrete mixing step is excluded because the same amount of water is consumed in a classical concrete manufacturing process.

Commercial Air Pumps (EcoPlus Eco Air 7, each with a power of 200 W) are used for CO 2 injection into the suspension, and their energy consumption is duly considered for the developed carbonation approach.

Each kWh of electricity consumption emits 0.39 kg CO 2 -eq, in alignment with the average value of the US electricity grid 68 .

Irrespective of whether concrete derives from a functional unit of cement carbonated with the proposed approach or not, its following use in practice is assumed to be the same. Therefore, the CO 2 emissions associated with concrete use and recycling are excluded.

A CO 2 injection volume of 8000 scc per 50 g cement is considered as a reference for the carbonation approach. The corresponding CO 2 capture rate of 26.2% (i.e., the lower capture rate achieved in the laboratory experiments for a CO 2 injection lasting 40 min) is also considered.

The continuous mixing process of the suspension-based fresh concrete carbonation approach is considered a part of the mixing process with subsequent concrete mixing with additional cement and aggregates; thus, it is excluded from the calculation.

Data availability

The raw data in support of most of the quantitative figures reported in this work are reported in the Supplementary Information. All of the other data are available from the corresponding author upon reasonable request.

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Acknowledgements

The authors would like to acknowledge CEMEX Innovation Holding Ltd. for its financial support. The authors would also like to acknowledge the NUANCE Center and IMSERC at Northwestern University. This work made use of the EPIC facility of Northwestern University’s NUANCE Center, which has received support from the SHyNE Resource (NSF ECCS-2025633), the IIN, and Northwestern’s MRSEC program (NSF DMR-1720139). This work made use of the IMSERC Physical Characterization facility at Northwestern University, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS-2025633), and Northwestern University.

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Fu, X., Guerini, A., Zampini, D. et al. Storing CO 2 while strengthening concrete by carbonating its cement in suspension. Commun Mater 5 , 109 (2024). https://doi.org/10.1038/s43246-024-00546-9

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• Volume 10, Issue 2
• Heavy resistance training at retirement age induces 4-year lasting beneficial effects in muscle strength: a long-term follow-up of an RCT
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• http://orcid.org/0009-0007-9331-6790 Mads Bloch-Ibenfeldt 1 , 2 ,
• Anne Theil Gates 1 , 2 ,
• Karoline Karlog 1 ,
• Naiara Demnitz 3 ,
• Michael Kjaer 1 , 4 ,
• Carl-Johan Boraxbekk 1 , 4 , 5
• 1 Department of Orthopedic Surgery M81 , Institute of Sports Medicine Copenhagen (ISMC), Bispebjerg Hospital , Copenhagen , Denmark
• 2 Center for Healthy Aging , Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark
• 3 Danish Research Centre for Magnetic Resonance (DRCMR), Centre for Functional and Diagnostic Imaging and Research , Copenhagen University Hospital - Amager and Hvidovre , Copenhagen , Denmark
• 4 Institute for Clinical Medicine , Faculty of Health and Medical Sciences, University of Copenhagen , Copenhagen , Denmark
• 5 Department of Neurology , Copenhagen University Hospital - Bispebjerg and Frederiksberg , Copenhagen , Denmark
• Correspondence to Mads Bloch-Ibenfeldt; mads.bloch-ibenfeldt{at}regionh.dk

Objectives Muscle function and size decline with age, but long-term effects of resistance training in older adults are largely unknown. Here, we explored the long-lasting (3 years) effects of 1 year of supervised resistance training with heavy loads.

Methods The LIve active Successful Ageing (LISA) study was a parallel group randomised controlled trial at a university hospital in Denmark. Older adults (n=451) at retirement age were randomised to 1 year of heavy resistance training (HRT), moderate-intensity training (MIT) or a non-exercising control group (CON). Primary outcome measure was leg extensor power. Secondary outcomes included maximal isometric quadriceps torque (isometric leg strength) and body composition (dual-energy X-ray absorptiometry (DXA)). Participants completed test procedures at baseline, following the 1-year intervention, and 2 and 4 years post study start.

Conclusion In well-functioning older adults at retirement age, 1 year of HRT may induce long-lasting beneficial effects by preserving muscle function.

Trial registration number NCT02123641 .

• Body composition
• Skeletal muscle

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:  http://creativecommons.org/licenses/by-nc/4.0/ .

https://doi.org/10.1136/bmjsem-2024-001899

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WHAT IS ALREADY KNOWN ON THIS TOPIC

Worldwide, the ageing population is growing. Unfortunately, skeletal muscle function and autonomy decrease with increased age. Thus, a challenge for society is to promote a healthy lifespan without age-related diseases and loss of autonomy.

WHAT THIS STUDY ADDS

Despite relatively healthy and well-functioning participants, 1 year of heavy resistance training at retirement age resulted in maintained strength 4 years after the study started. We propose that higher load resistance training may play an important role to induce long-lasting adaptations.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

This study provides evidence that resistance training with heavy loads at retirement age can have long-term effects over several years. The results, therefore, provide means for practitioners and policy-makers to encourage older individuals to engage in heavy resistance training.

Introduction

Skeletal muscle function declines with advancing age. 1–3 Although resistance training may partly counteract loss of muscle mass and function, shorter training studies (6–9 months duration) only show somewhat preserved muscle mass and function at 6–12 months follow-up. 4 5 Unfortunately, long-term follow-ups are sparse. 6 In one study, strength gains following high-intensity resistance training, and not low-intensity training, were preserved after 48 weeks of detraining. 7 The LIve active Successful Ageing (LISA) study, a large-scale randomised controlled trial (n=451), showed that strength can be maintained over 12 months following 1 year of heavy resistance training (HRT), but not after moderate training. 8 Thus, to gain long-lasting effects of resistance training in ageing one could speculate that high intensity or heavy loads are required. Here, we investigated whether there would be long-lasting effects of a 1-year supervised resistance training regimen with heavy loads, 3 years following the training in older individuals at retirement age.

Intervention

The current manuscript is an interim analysis of the LISA study, and additional follow-ups are planned (7-year and 10-year follow-ups). For details of intervention, recruitment and power calculations, see previous publications. 9 10 Briefly, 451 older adults were stratified according to sex, body mass index (BMI) and chair-rise test performance and randomised to 1 year of training with either heavy loads (HRT, n=149), moderate-intensity training (MIT, n=154) or a control condition (CON, n=148). At a commercial gym, HRT performed a supervised full body programme three times per week, with 6–8 weeks of initial habituation. The periodisation programme was machine based and each exercise included 3 sets of 6–12 repetitions at ~70%–85% of 1 RM, which was estimated using the prediction equation according to methods by Brzycki. 11 12 The moderate training in MIT was performed as circuit training with body weight and resistance bands once per week at the hospital and two times per week at home. Exercises in MIT progressed with the load of resistance bands (TheraBand, Akron, Ohio, USA) and mimicked the exercises in HRT but were performed with 3 sets of 10–18 repetitions at ~50%–60% of 1 RM. Both training programmes were created to comply with recommended guidelines 13 and included nine exercises—see published study protocol for full details. 10 Individuals in CON were encouraged to maintain their habitual physical activity level and were invited to regular cultural and social activities. In general, participants did not receive advice on healthy behaviour but were aware of the study timeline and planned follow-ups.

Test procedures

Day 1 included a health screening. On day 2, participants were dual-energy X-ray absorptiometry (DXA) scanned. Visceral fat mass was estimated by scanner software (Lunar iDXA, GE HealthCare—enCORE software V.16). Isometric leg strength (quadriceps) was assessed in a Good Strength chair (Bluetooth V.3.14, Metitur) and maximal isometric quadriceps torque (Newton metres) was measured during a minimum of 3 attempts per leg. 14 15 Day 3 included MRI of the brain and thigh (two-dimensional T1-weighted, 3.0 Tesla Phillips Achieva). Blinded assessors determined CSA of m. vastus lateralis using JIM software (Xinapse systems).

Daily physical activity was assessed as daily step count between days 2 and 3, by an accelerometer (activPAL micro, PAL Technologies) worn by the participants for five consecutive days. The test procedures were performed at baseline, postintervention (year 1) and at 2-year and 4-year follow-ups.

Patient and public involvement

Participants were informed of study progress through newsletters, and received overviews of personal results after tests at each time point. Additionally, participants were invited to an information evening, where the general study results at the time were presented.

Statistical analysis

Statistical analyses were performed in R V.4.1.1 and Rstudio 2021.09.0 using ‘psych’, 16 ‘emmeans’ 17 and ‘sjstats’ 18 packages. Figures were created in GraphPad Prism V.10.0.3.

At year 4, 369 participants attended follow-up assessments (HRT, n=128; MIT, n=126; CON, n=115). 82 older adults dropped out primarily due to lack of motivation or severe illness. These individuals had higher body weight, BMI and waist circumference at baseline compared with participants who were still part of the study at year 4. However, there was no difference in the response to the intervention in all outcomes at year 1 assessments between participants and individuals subsequently lost to follow-up. On average, participants were 71 years old (range: 64–75 years), 61% women and still active based on the daily physical activity ( table 1 ). There was no difference in sample characteristics between groups at baseline or at follow-up.

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Sample characteristics (mean±SD), n=369 unless otherwise specified

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(A–C) Isometric strength (mean±SEM) across 4 years for the different groups (heavy resistance training, HRT, moderate-intensity training, MIT and control group, CON). (A) (n=353) Isometric leg strength (Nm) trajectories for all time points separated by group. (B) Baseline and 4-year follow-up data (n=362), each group shown separately. (C) Individual data points showing the distribution of change from baseline to year four separated by group. *Significantly different from baseline (A): HRT 1 year, p<0.001; MIT 1 year, p=0.01; HRT 2 years, p<0.001; CON 4 years, p<0.001) (B): MIT 4 years, p=0.01; CON 4 years, p<0.001). #Change from baseline significantly different from change in MIT (A): HRT 4 years, p=0.003) (B): HRT 4 years, p=0.03). $Change from baseline significantly different from change in CON (A): HRT 4 years, p<0.001) (B): HRT 4 years, p<0.001).

In the change from baseline to year 4 ( figure 1B ), muscle strength was decreased in MIT (t(122)=1.98, p=0.01) and in CON (t(113)=1.98, p<0.001), whereas it was maintained in HRT (t(124)=1.98, p=0.37).

(A–B) Lean body mass and visceral fat (mean±SEM) across 4 years for the different groups (heavy resistance training, HRT, moderate-intensity training, MIT and control group, CON). (A) (n=365) Lean body mass (kg) trajectories for all time points separated by group. (B) Visceral fat (g) trajectories (n=365), for all time points separated by group. *Significantly different from baseline (A): HRT 1 year, p<0.001; MIT 4 years, p<0.001; CON 4 years, p=0.003) (B): HRT 1 year, p=0.01; CON 4 years, p=0.04).

Significant group×time interactions for CSA of m. vastus lateralis and the percentage of total body fat ( table 2 ) were driven by 1-year and 2-year changes, which have been reported previously. 8 9

Outcome variables (mean±SD) at baseline and at 4 years separated by group

For leg extensor power, handgrip strength and lean leg mass, there was a main effect of time, with decreases over the 4 years across all groups, but no interaction effects or significant group differences for the Δchange over 4 years ( table 2 ).

Resistance training with heavy loads induced long-lasting beneficial effects on muscle strength in a sample of older adults. We observed a difference between groups in leg strength, whereas handgrip strength, a measure of overall muscle strength, 19 was not influenced by any of the training regimes. Notably, benefits in leg strength were present despite lowered leg lean mass. Neural adaptations influence the response to resistance training. 20 21 The present results suggest that these adaptations might play a role even as lean leg mass and thigh CSA decrease. This is in line with a recent report showing that prolonged training across the lifespan is associated with permanently elevated acetylcholine receptors and improved neuromuscular function. 22 Resistance training may, therefore, be beneficial for function beyond the influence of muscle size itself.

Despite no group effects in lean leg mass, HRT maintained total lean mass, yet differences were minor. Interestingly, leg muscle strength was maintained from baseline in HRT, indicating that among individuals who already seemed to have a high physical activity level but were previously resistance training naive, implementing resistance training with heavy loads for 1 year may at group-level induce long-term health effects. Considering that muscle strength has been shown to predict mortality in apparently healthy populations, 23 these results may be of particular relevance. It is somewhat surprising that there was no muscular effect of the moderate training at year 4, as the intervention improved both lean mass and function in MIT, although to a lesser extent than HRT.

Interestingly, the amount of visceral fat was maintained from baseline to year 4 in both training groups, implying that some parameters may not be load-dependent or intensity-dependent in the long term. Recent research suggests that visceral fat is positively affected by resistance training. 24 Like visceral fat, the decrease over time in leg extensor power (primary outcome measure) was in line with our previous studies. 8 9

The present study benefited from its large sample size, long intervention and multiple follow-ups. Further, study attendance remained high (82% at year 4). Of note, with almost 10 000 daily steps, the study sample is likely to be healthier and more active than the average ageing population. Even so, ≈80% of the participants had at least one chronic medical disease. 9 In age-matched older individuals living in residential care facilities, high-intensity functional training has proven effective in improving independence in activities of daily living. Although over 4 months, these results show further evidence of the effectiveness of high-intensity training in older adults. 25

In conclusion, we showed that in a group of well-functioning older adults around retirement age, 1 year of HRT may induce long-lasting beneficial effects by preserving muscle function.

Ethics statements

Patient consent for publication.

Not applicable.

Ethics approval

This study involves human participants and was approved by Regional ethics committee: Capital Region, Copenhagen, Denmark, No. H-3-2014-017. Participants gave informed consent to participate in the study before taking part.

Acknowledgments

The authors thank Sussi Larsen, Kenneth Hudlebusch Mertz, Christian Skou Eriksen and Andreas Kraag Ziegler for helping with data collection.

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Supplementary materials

• Press release

Contributors Conceptualisation: MK; Methodology: MK and C-JB; Validation: MB-I, ATG, KK, ND, MK and C-JB; Formal analysis: MB-I and ND; Investigation: MB-I, ATG and KK; Visualisation: MB-I; Supervision: MK and C-JB; Project administration: MB-I and ATG; Writing–original draft: MB-I; Writing–review and editing: MB-I, ATG, KK, ND, MK and C-JB. All authors approved the final manuscript to be published.

Funding Lundbeck Foundation (R380-2021-1269) and supported by Nordea Foundation (Grant from Center for Healthy Aging, University of Copenhagen, Denmark).

Competing interests None declared.

Provenance and peer review Not commissioned; externally peer reviewed.

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Barbosa, Humberto A., Catarina O. Buriti, and T. V. Lakshmi Kumar. 2024. "Deep Learning for Flash Drought Detection: A Case Study in Northeastern Brazil" Atmosphere 15, no. 7: 761. https://doi.org/10.3390/atmos15070761

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