When we began this process, we were doctoral students and a faculty member in a research methods course. As students, we were facing a review of the literature for our dissertations. We encountered several different ways of conducting a review but were unable to locate any resources that synthesized all of the various synthesis methodologies. Our purpose is to present a comprehensive overview and assessment of the main approaches to research synthesis. We use ‘research synthesis’ as a broad overarching term to describe various approaches to combining, integrating, and synthesizing research findings.
We conducted an integrative review of the literature to explore the historical, contextual, and evolving nature of research synthesis. We searched five databases, reviewed websites of key organizations, hand-searched several journals, and examined relevant texts from the reference lists of the documents we had already obtained.
We identified four broad categories of research synthesis methodology including conventional, quantitative, qualitative, and emerging syntheses. Each of the broad categories was compared to the others on the following: key characteristics, purpose, method, product, context, underlying assumptions, unit of analysis, strengths and limitations, and when to use each approach.
The current state of research synthesis reflects significant advancements in emerging synthesis studies that integrate diverse data types and sources. New approaches to research synthesis provide a much broader range of review alternatives available to health and social science students and researchers.
Since the turn of the century, public health emergencies have been identified worldwide, particularly related to infectious diseases. For example, the Severe Acute Respiratory Syndrome (SARS) epidemic in Canada in 2002-2003, the recent Ebola epidemic in Africa, and the ongoing HIV/AIDs pandemic are global health concerns. There have also been dramatic increases in the prevalence of chronic diseases around the world [1] – [3] . These epidemiological challenges have raised concerns about the ability of health systems worldwide to address these crises. As a result, public health systems reform has been initiated in a number of countries. In Canada, as in other countries, the role of evidence to support public health reform and improve population health has been given high priority. Yet, there continues to be a significant gap between the production of evidence through research and its application in practice [4] – [5] . One strategy to address this gap has been the development of new research synthesis methodologies to deal with the time-sensitive and wide ranging evidence needs of policy makers and practitioners in all areas of health care, including public health.
As doctoral nursing students facing a review of the literature for our dissertations, and as a faculty member teaching a research methods course, we encountered several ways of conducting a research synthesis but found no comprehensive resources that discussed, compared, and contrasted various synthesis methodologies on their purposes, processes, strengths and limitations. To complicate matters, writers use terms interchangeably or use different terms to mean the same thing, and the literature is often contradictory about various approaches. Some texts [6] , [7] – [9] did provide a preliminary understanding about how research synthesis had been taken up in nursing, but these did not meet our requirements. Thus, in this article we address the need for a comprehensive overview of research synthesis methodologies to guide public health, health care, and social science researchers and practitioners.
Research synthesis is relatively new in public health but has a long history in other fields dating back to the late 1800s. Research synthesis, a research process in its own right [10] , has become more prominent in the wake of the evidence-based movement of the 1990s. Research syntheses have found their advocates and detractors in all disciplines, with challenges to the processes of systematic review and meta-analysis, in particular, being raised by critics of evidence-based healthcare [11] – [13] .
Our purpose was to conduct an integrative review of the literature to explore the historical, contextual, and evolving nature of research synthesis [14] – [15] . We synthesize and critique the main approaches to research synthesis that are relevant for public health, health care, and social scientists. Research synthesis is the overarching term we use to describe approaches to combining, aggregating, integrating, and synthesizing primary research findings. Each synthesis methodology draws on different types of findings depending on the purpose and product of the chosen synthesis (see Additional File 1 ).
Based on our current knowledge of the literature, we identified these approaches to include in our review: systematic review, meta-analysis, qualitative meta-synthesis, meta-narrative synthesis, scoping review, rapid review, realist synthesis, concept analysis, literature review, and integrative review. Our first step was to divide the synthesis types among the research team. Each member did a preliminary search to identify key texts. The team then met to develop search terms and a framework to guide the review.
Over the period of 2008 to 2012 we extensively searched the literature, updating our search at several time points, not restricting our search by date. The dates of texts reviewed range from 1967 to 2015. We used the terms above combined with the term “method* (e.g., “realist synthesis” and “method*) in the database Health Source: Academic Edition (includes Medline and CINAHL). This search yielded very few texts on some methodologies and many on others. We realized that many documents on research synthesis had not been picked up in the search. Therefore, we also searched Google Scholar, PubMed, ERIC, and Social Science Index, as well as the websites of key organizations such as the Joanna Briggs Institute, the University of York Centre for Evidence-Based Nursing, and the Cochrane Collaboration database. We hand searched several nursing, social science, public health and health policy journals. Finally, we traced relevant documents from the references in obtained texts.
We included works that met the following inclusion criteria: (1) published in English; (2) discussed the history of research synthesis; (3) explicitly described the approach and specific methods; or (4) identified issues, challenges, strengths and limitations of the particular methodology. We excluded research reports that resulted from the use of particular synthesis methodologies unless they also included criteria 2, 3, or 4 above.
Based on our search, we identified additional types of research synthesis (e.g., meta-interpretation, best evidence synthesis, critical interpretive synthesis, meta-summary, grounded formal theory). Still, we missed some important developments in meta-analysis, for example, identified by the journal's reviewers that have now been discussed briefly in the paper. The final set of 197 texts included in our review comprised theoretical, empirical, and conceptual papers, books, editorials and commentaries, and policy documents.
In our preliminary review of key texts, the team inductively developed a framework of the important elements of each method for comparison. In the next phase, each text was read carefully, and data for these elements were extracted into a table for comparison on the points of: key characteristics, purpose, methods, and product; see Additional File 1 ). Once the data were grouped and extracted, we synthesized across categories based on the following additional points of comparison: complexity of the process, degree of systematization, consideration of context, underlying assumptions, unit of analysis, and when to use each approach. In our results, we discuss our comparison of the various synthesis approaches on the elements above. Drawing only on documents for the review, ethics approval was not required.
We identified four broad categories of research synthesis methodology: Conventional, quantitative, qualitative, and emerging syntheses. From our dataset of 197 texts, we had 14 texts on conventional synthesis, 64 on quantitative synthesis, 78 on qualitative synthesis, and 41 on emerging syntheses. Table 1 provides an overview of the four types of research synthesis, definitions, types of data used, products, and examples of the methodology.
Types of Research Synthesis | Definition | Data Types Used | Products | Examples |
1. Conventional Synthesis | Older forms of review with less-systematic examination, critique, and synthesis of the literature on a mature topic for re-conceptulization or on a new topic for preliminary conceptualization | , – | ||
2. Quantitative Synthesis | Combining, aggregating, or integrating quantitative empirical research with data expressed in numeric form | , – – – | ||
3. Qualitative Synthesis | Combining, aggregating, or integrating qualitative empirical research and/or theoretical work expressed in narrative form | – – , – , , – , – – , – – , – | ||
4. Emerging Synthesis | Newer syntheses that provide a systematic approach to synthesizing varied literature in a topic area that includes diverse data types | – – – – , , – |
Although we group these types of synthesis into four broad categories on the basis of similarities, each type within a category has unique characteristics, which may differ from the overall group similarities. Each could be explored in greater depth to tease out their unique characteristics, but detailed comparison is beyond the scope of this article.
Additional File 1 presents one or more selected types of synthesis that represent the broad category but is not an exhaustive presentation of all types within each category. It provides more depth for specific examples from each category of synthesis on the characteristics, purpose, methods, and products than is found in Table 1 .
4.1.1. what is it.
Here we draw on two types of categorization. First, we utilize Dixon Woods et al.'s [49] classification of research syntheses as being either integrative or interpretive . (Please note that integrative syntheses are not the same as an integrative review as defined in Additional File 1 .) Second, we use Popay's [80] enhancement and epistemological models .
The defining characteristics of integrative syntheses are that they involve summarizing the data achieved by pooling data [49] . Integrative syntheses include systematic reviews, meta-analyses, as well as scoping and rapid reviews because each of these focus on summarizing data. They also define concepts from the outset (although this may not always be true in scoping or rapid reviews) and deal with a well-specified phenomenon of interest.
Interpretive syntheses are primarily concerned with the development of concepts and theories that integrate concepts [49] . The analysis in interpretive synthesis is conceptual both in process and outcome, and “the product is not aggregations of data, but theory” [49] , [p.12]. Interpretive syntheses involve induction and interpretation, and are primarily conceptual in process and outcome. Examples include integrative reviews, some systematic reviews, all of the qualitative syntheses, meta-narrative, realist and critical interpretive syntheses. Of note, both quantitative and qualitative studies can be either integrative or interpretive
The second categorization, enhancement versus epistemological , applies to those approaches that use multiple data types and sources [80] . Popay's [80] classification reflects the ways that qualitative data are valued in relation to quantitative data.
In the enhancement model , qualitative data adds something to quantitative analysis. The enhancement model is reflected in systematic reviews and meta-analyses that use some qualitative data to enhance interpretation and explanation. It may also be reflected in some rapid reviews that draw on quantitative data but use some qualitative data.
The epistemological model assumes that quantitative and qualitative data are equal and each has something unique to contribute. All of the other review approaches, except pure quantitative or qualitative syntheses, reflect the epistemological model because they value all data types equally but see them as contributing different understandings.
By and large, the quantitative approaches (quantitative systematic review and meta-analysis) have typically used purely quantitative data (i.e., expressed in numeric form). More recently, both Cochrane [81] and Campbell [82] collaborations are grappling with the need to, and the process of, integrating qualitative research into a systematic review. The qualitative approaches use qualitative data (i.e., expressed in words). All of the emerging synthesis types, as well as the conventional integrative review, incorporate qualitative and quantitative study designs and data.
Four types of research questions direct inquiry across the different types of syntheses. The first is a well-developed research question that gives direction to the synthesis (e.g., meta-analysis, systematic review, meta-study, concept analysis, rapid review, realist synthesis). The second begins as a broad general question that evolves and becomes more refined over the course of the synthesis (e.g., meta-ethnography, scoping review, meta-narrative, critical interpretive synthesis). In the third type, the synthesis begins with a phenomenon of interest and the question emerges in the analytic process (e.g., grounded formal theory). Lastly, there is no clear question, but rather a general review purpose (e.g., integrative review). Thus, the requirement for a well-defined question cuts across at least three of the synthesis types (e.g., quantitative, qualitative, and emerging).
This is a contested issue within and between the four synthesis categories. There are strong proponents of quality appraisal in the quantitative traditions of systematic review and meta-analysis based on the need for strong studies that will not jeopardize validity of the overall findings. Nonetheless, there is no consensus on pre-defined criteria; many scales exist that vary dramatically in composition. This has methodological implications for the credibility of findings [83] .
Specific methodologies from the conventional, qualitative, and emerging categories support quality appraisal but do so with caveats. In conventional integrative reviews appraisal is recommended, but depends on the sampling frame used in the study [18] . In meta-study, appraisal criteria are explicit but quality criteria are used in different ways depending on the specific requirements of the inquiry [54] . Among the emerging syntheses, meta-narrative review developers support appraisal of a study based on criteria from the research tradition of the primary study [67] , [84] – [85] . Realist synthesis similarly supports the use of high quality evidence, but appraisal checklists are viewed with scepticism and evidence is judged based on relevance to the research question and whether a credible inference may be drawn [69] . Like realist, critical interpretive syntheses do not judge quality using standardized appraisal instruments. They will exclude fatally flawed studies, but there is no consensus on what ‘fatally flawed’ means [49] , [71] . Appraisal is based on relevance to the inquiry, not rigor of the study.
There is no agreement on quality appraisal among qualitative meta-ethnographers with some supporting and others refuting the need for appraisal. [60] , [62] . Opponents of quality appraisal are found among authors of qualitative (grounded formal theory and concept analysis) and emerging syntheses (scoping and rapid reviews) because quality is not deemed relevant to the intention of the synthesis; the studies being reviewed are not effectiveness studies where quality is extremely important. These qualitative synthesis are often reviews of theoretical developments where the concept itself is what is important, or reviews that provide quotations from the raw data so readers can make their own judgements about the relevance and utility of the data. For example, in formal grounded theory, the purpose of theory generation and authenticity of data used to generate the theory is not as important as the conceptual category. Inaccuracies may be corrected in other ways, such as using the constant comparative method, which facilitates development of theoretical concepts that are repeatedly found in the data [86] – [87] . For pragmatic reasons, evidence is not assessed in rapid and scoping reviews, in part to produce a timely product. The issue of quality appraisal is unresolved across the terrain of research synthesis and we consider this further in our discussion.
All research syntheses share a common purpose -- to summarize, synthesize, or integrate research findings from diverse studies. This helps readers stay abreast of the burgeoning literature in a field. Our discussion here is at the level of the four categories of synthesis. Beginning with conventional literature syntheses, the overall purpose is to attend to mature topics for the purpose of re-conceptualization or to new topics requiring preliminary conceptualization [14] . Such syntheses may be helpful to consider contradictory evidence, map shifting trends in the study of a phenomenon, and describe the emergence of research in diverse fields [14] . The purpose here is to set the stage for a study by identifying what has been done, gaps in the literature, important research questions, or to develop a conceptual framework to guide data collection and analysis.
The purpose of quantitative systematic reviews is to combine, aggregate, or integrate empirical research to be able to generalize from a group of studies and determine the limits of generalization [27] . The focus of quantitative systematic reviews has been primarily on aggregating the results of studies evaluating the effectiveness of interventions using experimental, quasi-experimental, and more recently, observational designs. Systematic reviews can be done with or without quantitative meta-analysis but a meta-analysis always takes place within the context of a systematic review. Researchers must consider the review's purpose and the nature of their data in undertaking a quantitative synthesis; this will assist in determining the approach.
The purpose of qualitative syntheses is broadly to synthesize complex health experiences, practices, or concepts arising in healthcare environments. There may be various purposes depending on the qualitative methodology. For example, in hermeneutic studies the aim may be holistic explanation or understanding of a phenomenon [42] , which is deepened by integrating the findings from multiple studies. In grounded formal theory, the aim is to produce a conceptual framework or theory expected to be applicable beyond the original study. Although not able to generalize from qualitative research in the statistical sense [88] , qualitative researchers usually do want to say something about the applicability of their synthesis to other settings or phenomena. This notion of ‘theoretical generalization’ has been referred to as ‘transferability’ [89] – [90] and is an important criterion of rigour in qualitative research. It applies equally to the products of a qualitative synthesis in which the synthesis of multiple studies on the same phenomenon strengthens the ability to draw transferable conclusions.
The overarching purpose of emerging syntheses is challenging the more traditional types of syntheses, in part by using data from both quantitative and qualitative studies with diverse designs for analysis. Beyond this, however, each emerging synthesis methodology has a unique purpose. In meta-narrative review, the purpose is to identify different research traditions in the area, synthesize a complex and diverse body of research. Critical interpretive synthesis shares this characteristic. Although a distinctive approach, critical interpretive synthesis utilizes a modification of the analytic strategies of meta-ethnography [61] (e.g., reciprocal translational analysis, refutational synthesis, and lines of argument synthesis) but goes beyond the use of these to bring a critical perspective to bear in challenging the normative or epistemological assumptions in the primary literature [72] – [73] . The unique purpose of a realist synthesis is to amalgamate complex empirical evidence and theoretical understandings within a diverse body of literature to uncover the operative mechanisms and contexts that affect the outcomes of social interventions. In a scoping review, the intention is to find key concepts, examine the range of research in an area, and identify gaps in the literature. The purpose of a rapid review is comparable to that of a scoping review, but done quickly to meet the time-sensitive information needs of policy makers.
4.3.1. degree of systematization.
There are varying degrees of systematization across the categories of research synthesis. The most systematized are quantitative systematic reviews and meta-analyses. There are clear processes in each with judgments to be made at each step, although there are no agreed upon guidelines for this. The process is inherently subjective despite attempts to develop objective and systematic processes [91] – [92] . Mullen and Ramirez [27] suggest that there is often a false sense of rigour implied by the terms ‘systematic review’ and ‘meta-analysis’ because of their clearly defined procedures.
In comparison with some types of qualitative synthesis, concept analysis is quite procedural. Qualitative meta-synthesis also has defined procedures and is systematic, yet perhaps less so than concept analysis. Qualitative meta-synthesis starts in an unsystematic way but becomes more systematic as it unfolds. Procedures and frameworks exist for some of the emerging types of synthesis [e.g., [50] , [63] , [71] , [93] ] but are not linear, have considerable flexibility, and are often messy with emergent processes [85] . Conventional literature reviews tend not to be as systematic as the other three types. In fact, the lack of systematization in conventional literature synthesis was the reason for the development of more systematic quantitative [17] , [20] and qualitative [45] – [46] , [61] approaches. Some authors in the field [18] have clarified processes for integrative reviews making them more systematic and rigorous, but most conventional syntheses remain relatively unsystematic in comparison with other types.
Some synthesis processes are considerably more complex than others. Methodologies with clearly defined steps are arguably less complex than the more flexible and emergent ones. We know that any study encounters challenges and it is rare that a pre-determined research protocol can be followed exactly as intended. Not even the rigorous methods associated with Cochrane [81] systematic reviews and meta-analyses are always implemented exactly as intended. Even when dealing with numbers rather than words, interpretation is always part of the process. Our collective experience suggests that new methodologies (e.g., meta-narrative synthesis and realist synthesis) that integrate different data types and methods are more complex than conventional reviews or the rapid and scoping reviews.
The products of research syntheses usually take three distinct formats (see Table 1 and Additional File 1 for further details). The first representation is in tables, charts, graphical displays, diagrams and maps as seen in integrative, scoping and rapid reviews, meta-analyses, and critical interpretive syntheses. The second type of synthesis product is the use of mathematical scores. Summary statements of effectiveness are mathematically displayed in meta-analyses (as an effect size), systematic reviews, and rapid reviews (statistical significance).
The third synthesis product may be a theory or theoretical framework. A mid-range theory can be produced from formal grounded theory, meta-study, meta-ethnography, and realist synthesis. Theoretical/conceptual frameworks or conceptual maps may be created in meta-narrative and critical interpretive syntheses, and integrative reviews. Concepts for use within theories are produced in concept analysis. While these three product types span the categories of research synthesis, narrative description and summary is used to present the products resulting from all methodologies.
There are diverse ways that context is considered in the four broad categories of synthesis. Context may be considered to the extent that it features within primary studies for the purpose of the review. Context may also be understood as an integral aspect of both the phenomenon under study and the synthesis methodology (e.g., realist synthesis). Quantitative systematic reviews and meta-analyses have typically been conducted on studies using experimental and quasi-experimental designs and more recently observational studies, which control for contextual features to allow for understanding of the ‘true’ effect of the intervention [94] .
More recently, systematic reviews have included covariates or mediating variables (i.e., contextual factors) to help explain variability in the results across studies [27] . Context, however, is usually handled in the narrative discussion of findings rather than in the synthesis itself. This lack of attention to context has been one criticism leveled against systematic reviews and meta-analyses, which restrict the types of research designs that are considered [e.g., [95] ].
When conventional literature reviews incorporate studies that deal with context, there is a place for considering contextual influences on the intervention or phenomenon. Reviews of quantitative experimental studies tend to be devoid of contextual considerations since the original studies are similarly devoid, but context might figure prominently in a literature review that incorporates both quantitative and qualitative studies.
Qualitative syntheses have been conducted on the contextual features of a particular phenomenon [33] . Paterson et al. [54] advise researchers to attend to how context may have influenced the findings of particular primary studies. In qualitative analysis, contextual features may form categories by which the data can be compared and contrasted to facilitate interpretation. Because qualitative research is often conducted to understand a phenomenon as a whole, context may be a focus, although this varies with the qualitative methodology. At the same time, the findings in a qualitative synthesis are abstracted from the original reports and taken to a higher level of conceptualization, thus removing them from the original context.
Meta-narrative synthesis [67] , [84] , because it draws on diverse research traditions and methodologies, may incorporate context into the analysis and findings. There is not, however, an explicit step in the process that directs the analyst to consider context. Generally, the research question guiding the synthesis is an important factor in whether context will be a focus.
More recent iterations of concept analysis [47] , [96] – [97] explicitly consider context reflecting the assumption that a concept's meaning is determined by its context. Morse [47] points out, however, that Wilson's [98] approach to concept analysis, and those based on Wilson [e.g., [45] ], identify attributes that are devoid of context, while Rodgers' [96] , [99] evolutionary method considers context (e.g., antecedents, consequences, and relationships to other concepts) in concept development.
Realist synthesis [69] considers context as integral to the study. It draws on a critical realist logic of inquiry grounded in the work of Bhaskar [100] , who argues that empirical co-occurrence of events is insufficient for inferring causation. One must identify generative mechanisms whose properties are causal and, depending on the situation, may nor may not be activated [94] . Context interacts with program/intervention elements and thus cannot be differentiated from the phenomenon [69] . This approach synthesizes evidence on generative mechanisms and analyzes contextual features that activate them; the result feeds back into the context. The focus is on what works, for whom, under what conditions, why and how [68] .
When we began our review, we ‘assumed’ that the assumptions underlying synthesis methodologies would be a distinguishing characteristic of synthesis types, and that we could compare the various types on their assumptions, explicit or implicit. We found, however, that many authors did not explicate the underlying assumptions of their methodologies, and it was difficult to infer them. Kirkevold [101] has argued that integrative reviews need to be carried out from an explicit philosophical or theoretical perspective. We argue this should be true for all types of synthesis.
Authors of some emerging synthesis approaches have been very explicit about their assumptions and philosophical underpinnings. An implicit assumption of most emerging synthesis methodologies is that quantitative systematic reviews and meta-analyses have limited utility in some fields [e.g., in public health – [13] , [102] ] and for some kinds of review questions like those about feasibility and appropriateness versus effectiveness [103] – [104] . They also assume that ontologically and epistemologically, both kinds of data can be combined. This is a significant debate in the literature because it is about the commensurability of overarching paradigms [105] but this is beyond the scope of this review.
Realist synthesis is philosophically grounded in critical realism or, as noted above, a realist logic of inquiry [93] , [99] , [106] – [107] . Key assumptions regarding the nature of interventions that inform critical realism have been described above in the section on context. See Pawson et al. [106] for more information on critical realism, the philosophical basis of realist synthesis.
Meta-narrative synthesis is explicitly rooted in a constructivist philosophy of science [108] in which knowledge is socially constructed rather than discovered, and what we take to be ‘truth’ is a matter of perspective. Reality has a pluralistic and plastic character, and there is no pre-existing ‘real world’ independent of human construction and language [109] . See Greenhalgh et al. [67] , [85] and Greenhalgh & Wong [97] for more discussion of the constructivist basis of meta-narrative synthesis.
In the case of purely quantitative or qualitative syntheses, it may be an easier matter to uncover unstated assumptions because they are likely to be shared with those of the primary studies in the genre. For example, grounded formal theory shares the philosophical and theoretical underpinnings of grounded theory, rooted in the theoretical perspective of symbolic interactionism [110] – [111] and the philosophy of pragmatism [87] , [112] – [114] .
As with meta-narrative synthesis, meta-study developers identify constructivism as their interpretive philosophical foundation [54] , [88] . Epistemologically, constructivism focuses on how people construct and re-construct knowledge about a specific phenomenon, and has three main assumptions: (1) reality is seen as multiple, at times even incompatible with the phenomenon under consideration; (2) just as primary researchers construct interpretations from participants' data, meta-study researchers also construct understandings about the primary researchers' original findings. Thus, meta-synthesis is a construction of a construction, or a meta-construction; and (3) all constructions are shaped by the historical, social and ideological context in which they originated [54] . The key message here is that reports of any synthesis would benefit from an explicit identification of the underlying philosophical perspectives to facilitate a better understanding of the results, how they were derived, and how they are being interpreted.
The unit of analysis for each category of review is generally distinct. For the emerging synthesis approaches, the unit of analysis is specific to the intention. In meta-narrative synthesis it is the storyline in diverse research traditions; in rapid review or scoping review, it depends on the focus but could be a concept; and in realist synthesis, it is the theories rather than programs that are the units of analysis. The elements of theory that are important in the analysis are mechanisms of action, the context, and the outcome [107] .
For qualitative synthesis, the units of analysis are generally themes, concepts or theories, although in meta-study, the units of analysis can be research findings (“meta-data-analysis”), research methods (“meta-method”) or philosophical/theoretical perspectives (“meta-theory”) [54] . In quantitative synthesis, the units of analysis range from specific statistics for systematic reviews to effect size of the intervention for meta-analysis. More recently, some systematic reviews focus on theories [115] – [116] , therefore it depends on the research question. Similarly, within conventional literature synthesis the units of analysis also depend on the research purpose, focus and question as well as on the type of research methods incorporated into the review. What is important in all research syntheses, however, is that the unit of analysis needs to be made explicit. Unfortunately, this is not always the case.
In this section, we discuss the overarching strengths and limitations of synthesis methodologies as a whole and then highlight strengths and weaknesses across each of our four categories of synthesis.
With the vast proliferation of research reports and the increased ease of retrieval, research synthesis has become more accessible providing a way of looking broadly at the current state of research. The availability of syntheses helps researchers, practitioners, and policy makers keep up with the burgeoning literature in their fields without which evidence-informed policy or practice would be difficult. Syntheses explain variation and difference in the data helping us identify the relevance for our own situations; they identify gaps in the literature leading to new research questions and study designs. They help us to know when to replicate a study and when to avoid excessively duplicating research. Syntheses can inform policy and practice in a way that well-designed single studies cannot; they provide building blocks for theory that helps us to understand and explain our phenomena of interest.
The process of selecting, combining, integrating, and synthesizing across diverse study designs and data types can be complex and potentially rife with bias, even with those methodologies that have clearly defined steps. Just because a rigorous and standardized approach has been used does not mean that implicit judgements will not influence the interpretations and choices made at different stages.
In all types of synthesis, the quantity of data can be considerable, requiring difficult decisions about scope, which may affect relevance. The quantity of available data also has implications for the size of the research team. Few reviews these days can be done independently, in particular because decisions about inclusion and exclusion may require the involvement of more than one person to ensure reliability.
For all types of synthesis, it is likely that in areas with large, amorphous, and diverse bodies of literature, even the most sophisticated search strategies will not turn up all the relevant and important texts. This may be more important in some synthesis methodologies than in others, but the omission of key documents can influence the results of all syntheses. This issue can be addressed, at least in part, by including a library scientist on the research team as required by some funding agencies. Even then, it is possible to miss key texts. In this review, for example, because none of us are trained in or conduct meta-analyses, we were not even aware that we had missed some new developments in this field such as meta-regression [117] – [118] , network meta-analysis [119] – [121] , and the use of individual patient data in meta-analyses [122] – [123] .
One limitation of systematic reviews and meta-analyses is that they rapidly go out of date. We thought this might be true for all types of synthesis, although we wondered if those that produce theory might not be somewhat more enduring. We have not answered this question but it is open for debate. For all types of synthesis, the analytic skills and the time required are considerable so it is clear that training is important before embarking on a review, and some types of review may not be appropriate for students or busy practitioners.
Finally, the quality of reporting in primary studies of all genres is variable so it is sometimes difficult to identify aspects of the study essential for the synthesis, or to determine whether the study meets quality criteria. There may be flaws in the original study, or journal page limitations may necessitate omitting important details. Reporting standards have been developed for some types of reviews (e.g., systematic review, meta-analysis, meta-narrative synthesis, realist synthesis); but there are no agreed upon standards for qualitative reviews. This is an important area for development in advancing the science of research synthesis.
The conventional literature review and now the increasingly common integrative review remain important and accessible approaches for students, practitioners, and experienced researchers who want to summarize literature in an area but do not have the expertise to use one of the more complex methodologies. Carefully executed, such reviews are very useful for synthesizing literature in preparation for research grants and practice projects. They can determine the state of knowledge in an area and identify important gaps in the literature to provide a clear rationale or theoretical framework for a study [14] , [18] . There is a demand, however, for more rigour, with more attention to developing comprehensive search strategies and more systematic approaches to combining, integrating, and synthesizing the findings.
Generally, conventional reviews include diverse study designs and data types that facilitate comprehensiveness, which may be a strength on the one hand, but can also present challenges on the other. The complexity inherent in combining results from studies with diverse methodologies can result in bias and inaccuracies. The absence of clear guidelines about how to synthesize across diverse study types and data [18] has been a challenge for novice reviewers.
Quantitative systematic reviews and meta-analyses have been important in launching the field of evidence-based healthcare. They provide a systematic, orderly and auditable process for conducting a review and drawing conclusions [25] . They are arguably the most powerful approaches to understanding the effectiveness of healthcare interventions, especially when intervention studies on the same topic show very different results. When areas of research are dogged by controversy [25] or when study results go against strongly held beliefs, such approaches can reduce the uncertainty and bring strong evidence to bear on the controversy.
Despite their strengths, they also have limitations. Systematic reviews and meta-analyses do not provide a way of including complex literature comprising various types of evidence including qualitative studies, theoretical work, and epidemiological studies. Only certain types of design are considered and qualitative data are used in a limited way. This exclusion limits what can be learned in a topic area.
Meta-analyses are often not possible because of wide variability in study design, population, and interventions so they may have a narrow range of utility. New developments in meta-analysis, however, can be used to address some of these limitations. Network meta-analysis is used to explore relative efficacy of multiple interventions, even those that have never been compared in more conventional pairwise meta-analyses [121] , allowing for improved clinical decision making [120] . The limitation is that network meta-analysis has only been used in medical/clinical applications [119] and not in public health. It has not yet been widely accepted and many methodological challenges remain [120] – [121] . Meta-regression is another development that combines meta-analytic and linear regression principles to address the fact that heterogeneity of results may compromise a meta-analysis [117] – [118] . The disadvantage is that many clinicians are unfamiliar with it and may incorrectly interpret results [117] .
Some have accused meta-analysis of combining apples and oranges [124] raising questions in the field about their meaningfulness [25] , [28] . More recently, the use of individual rather than aggregate data has been useful in facilitating greater comparability among studies [122] . In fact, Tomas et al. [123] argue that meta-analysis using individual data is now the gold standard although access to the raw data from other studies may be a challenge to obtain.
The usefulness of systematic reviews in synthesizing complex health and social interventions has also been challenged [102] . It is often difficult to synthesize their findings because such studies are “epistemologically diverse and methodologically complex” [ [69] , p.21]. Rigid inclusion/exclusion criteria may allow only experimental or quasi-experimental designs into consideration resulting in lost information that may well be useful to policy makers for tailoring an intervention to the context or understanding its acceptance by recipients.
Qualitative syntheses may be the type of review most fraught with controversy and challenge, while also bringing distinct strengths to the enterprise. Although these methodologies provide a comprehensive and systematic review approach, they do not generally provide definitive statements about intervention effectiveness. They do, however, address important questions about the development of theoretical concepts, patient experiences, acceptability of interventions, and an understanding about why interventions might work.
Most qualitative syntheses aim to produce a theoretically generalizable mid-range theory that explains variation across studies. This makes them more useful than single primary studies, which may not be applicable beyond the immediate setting or population. All provide a contextual richness that enhances relevance and understanding. Another benefit of some types of qualitative synthesis (e.g., grounded formal theory) is that the concept of saturation provides a sound rationale for limiting the number of texts to be included thus making reviews potentially more manageable. This contrasts with the requirements of systematic reviews and meta-analyses that require an exhaustive search.
Qualitative researchers debate about whether the findings of ontologically and epistemological diverse qualitative studies can actually be combined or synthesized [125] because methodological diversity raises many challenges for synthesizing findings. The products of different types of qualitative syntheses range from theory and conceptual frameworks, to themes and rich descriptive narratives. Can one combine the findings from a phenomenological study with the theory produced in a grounded theory study? Many argue yes, but many also argue no.
Emerging synthesis methodologies were developed to address some limitations inherent in other types of synthesis but also have their own issues. Because each type is so unique, it is difficult to identify overarching strengths of the entire category. An important strength, however, is that these newer forms of synthesis provide a systematic and rigorous approach to synthesizing a diverse literature base in a topic area that includes a range of data types such as: both quantitative and qualitative studies, theoretical work, case studies, evaluations, epidemiological studies, trials, and policy documents. More than conventional literature reviews and systematic reviews, these approaches provide explicit guidance on analytic methods for integrating different types of data. The assumption is that all forms of data have something to contribute to knowledge and theory in a topic area. All have a defined but flexible process in recognition that the methods may need to shift as knowledge develops through the process.
Many emerging synthesis types are helpful to policy makers and practitioners because they are usually involved as team members in the process to define the research questions, and interpret and disseminate the findings. In fact, engagement of stakeholders is built into the procedures of the methods. This is true for rapid reviews, meta-narrative syntheses, and realist syntheses. It is less likely to be the case for critical interpretive syntheses.
Another strength of some approaches (realist and meta-narrative syntheses) is that quality and publication standards have been developed to guide researchers, reviewers, and funders in judging the quality of the products [108] , [126] – [127] . Training materials and online communities of practice have also been developed to guide users of realist and meta-narrative review methods [107] , [128] . A unique strength of critical interpretive synthesis is that it takes a critical perspective on the process that may help reconceptualize the data in a way not considered by the primary researchers [72] .
There are also challenges of these new approaches. The methods are new and there may be few published applications by researchers other than the developers of the methods, so new users often struggle with the application. The newness of the approaches means that there may not be mentors available to guide those unfamiliar with the methods. This is changing, however, and the number of applications in the literature is growing with publications by new users helping to develop the science of synthesis [e.g., [129] ]. However, the evolving nature of the approaches and their developmental stage present challenges for novice researchers.
Choosing an appropriate approach to synthesis will depend on the question you are asking, the purpose of the review, and the outcome or product you want to achieve. In Additional File 1 , we discuss each of these to provide guidance to readers on making a choice about review type. If researchers want to know whether a particular type of intervention is effective in achieving its intended outcomes, then they might choose a quantitative systemic review with or without meta-analysis, possibly buttressed with qualitative studies to provide depth and explanation of the results. Alternately, if the concern is about whether an intervention is effective with different populations under diverse conditions in varying contexts, then a realist synthesis might be the most appropriate.
If researchers' concern is to develop theory, they might consider qualitative syntheses or some of the emerging syntheses that produce theory (e.g., critical interpretive synthesis, realist review, grounded formal theory, qualitative meta-synthesis). If the aim is to track the development and evolution of concepts, theories or ideas, or to determine how an issue or question is addressed across diverse research traditions, then meta-narrative synthesis would be most appropriate.
When the purpose is to review the literature in advance of undertaking a new project, particularly by graduate students, then perhaps an integrative review would be appropriate. Such efforts contribute towards the expansion of theory, identify gaps in the research, establish the rationale for studying particular phenomena, and provide a framework for interpreting results in ways that might be useful for influencing policy and practice.
For researchers keen to bring new insights, interpretations, and critical re-conceptualizations to a body of research, then qualitative or critical interpretive syntheses will provide an inductive product that may offer new understandings or challenges to the status quo. These can inform future theory development, or provide guidance for policy and practice.
What is the current state of science regarding research synthesis? Public health, health care, and social science researchers or clinicians have previously used all four categories of research synthesis, and all offer a suitable array of approaches for inquiries. New developments in systematic reviews and meta-analysis are providing ways of addressing methodological challenges [117] – [123] . There has also been significant advancement in emerging synthesis methodologies and they are quickly gaining popularity. Qualitative meta-synthesis is still evolving, particularly given how new it is within the terrain of research synthesis. In the midst of this evolution, outstanding issues persist such as grappling with: the quantity of data, quality appraisal, and integration with knowledge translation. These topics have not been thoroughly addressed and need further debate.
We raise the question of whether it is possible or desirable to find all available studies for a synthesis that has this requirement (e.g., meta-analysis, systematic review, scoping, meta-narrative synthesis [25] , [27] , [63] , [67] , [84] – [85] ). Is the synthesis of all available studies a realistic goal in light of the burgeoning literature? And how can this be sustained in the future, particularly as the emerging methodologies continue to develop and as the internet facilitates endless access? There has been surprisingly little discussion on this topic and the answers will have far-reaching implications for searching, sampling, and team formation.
Researchers and graduate students can no longer rely on their own independent literature search. They will likely need to ask librarians for assistance as they navigate multiple sources of literature and learn new search strategies. Although teams now collaborate with library scientists, syntheses are limited in that researchers must make decisions on the boundaries of the review, in turn influencing the study's significance. The size of a team may also be pragmatically determined to manage the search, extraction, and synthesis of the burgeoning data. There is no single answer to our question about the possibility or necessity of finding all available articles for a review. Multiple strategies that are situation specific are likely to be needed.
While the issue of quality appraisal has received much attention in the synthesis literature, scholars are far from resolution. There may be no agreement about appraisal criteria in a given tradition. For example, the debate rages over the appropriateness of quality appraisal in qualitative synthesis where there are over 100 different sets of criteria and many do not overlap [49] . These differences may reflect disciplinary and methodological orientations, but diverse quality appraisal criteria may privilege particular types of research [49] . The decision to appraise is often grounded in ontological and epistemological assumptions. Nonetheless, diversity within and between categories of synthesis is likely to continue unless debate on the topic of quality appraisal continues and evolves toward consensus.
If research syntheses are to make a difference to practice and ultimately to improve health outcomes, then we need to do a better job of knowledge translation. In the Canadian Institutes of Health Research (CIHR) definition of knowledge translation (KT), research or knowledge synthesis is an integral component [130] . Yet, with few exceptions [131] – [132] , very little of the research synthesis literature even mentions the relationship of synthesis to KT nor does it discuss strategies to facilitate the integration of synthesis findings into policy and practice. The exception is in the emerging synthesis methodologies, some of which (e.g., realist and meta-narrative syntheses, scoping reviews) explicitly involve stakeholders or knowledge users. The argument is that engaging them in this way increases the likelihood that the knowledge generated will be translated into policy and practice. We suggest that a more explicit engagement with knowledge users in all types of synthesis would benefit the uptake of the research findings.
Research synthesis neither makes research more applicable to practice nor ensures implementation. Focus must now turn seriously towards translation of synthesis findings into knowledge products that are useful for health care practitioners in multiple areas of practice and develop appropriate strategies to facilitate their use. The burgeoning field of knowledge translation has, to some extent, taken up this challenge; however, the research-practice gap continues to plague us [133] – [134] . It is a particular problem for qualitative syntheses [131] . Although such syntheses have an important place in evidence-informed practice, little effort has gone into the challenge of translating the findings into useful products to guide practice [131] .
Our study took longer than would normally be expected for an integrative review. Each of us were primarily involved in our own dissertations or teaching/research positions, and so this study was conducted ‘off the sides of our desks.’ A limitation was that we searched the literature over the course of 4 years (from 2008–2012), necessitating multiple search updates. Further, we did not do a comprehensive search of the literature after 2012, thus the more recent synthesis literature was not systematically explored. We did, however, perform limited database searches from 2012–2015 to keep abreast of the latest methodological developments. Although we missed some new approaches to meta-analysis in our search, we did not find any new features of the synthesis methodologies covered in our review that would change the analysis or findings of this article. Lastly, we struggled with the labels used for the broad categories of research synthesis methodology because of our hesitancy to reinforce the divide between quantitative and qualitative approaches. However, it was very difficult to find alternative language that represented the types of data used in these methodologies. Despite our hesitancy in creating such an obvious divide, we were left with the challenge of trying to find a way of characterizing these broad types of syntheses.
Our findings offer methodological clarity for those wishing to learn about the broad terrain of research synthesis. We believe that our review makes transparent the issues and considerations in choosing from among the four broad categories of research synthesis. In summary, research synthesis has taken its place as a form of research in its own right. The methodological terrain has deep historical roots reaching back over the past 200 years, yet research synthesis remains relatively new to public health, health care, and social sciences in general. This is rapidly changing. New developments in systematic reviews and meta-analysis, and the emergence of new synthesis methodologies provide a vast array of options to review the literature for diverse purposes. New approaches to research synthesis and new analytic methods within existing approaches provide a much broader range of review alternatives for public health, health care, and social science students and researchers.
KSM is an assistant professor in the Faculty of Nursing at the University of Alberta. Her work on this article was largely conducted as a Postdoctoral Fellow, funded by KRESCENT (Kidney Research Scientist Core Education and National Training Program, reference #KRES110011R1) and the Faculty of Nursing at the University of Alberta.
MM's work on this study over the period of 2008-2014 was supported by a Canadian Institutes of Health Research Applied Public Health Research Chair Award (grant #92365).
We thank Rachel Spanier who provided support with reference formatting.
Conflict of interest: The authors declare that they have no conflicts of interest in this article.
Authors' contributions: KSM co-designed the study, collected data, analyzed the data, drafted/revised the manuscript, and managed the project.
MP contributed to searching the literature, developing the analytic framework, and extracting data for the Additional File.
JB contributed to searching the literature, developing the analytic framework, and extracting data for the Additional File.
WN contributed to searching the literature, developing the analytic framework, and extracting data for the Additional File.
All authors read and approved the final manuscript.
Additional Files: Additional File 1 – Selected Types of Research Synthesis
This Additional File is our dataset created to organize, analyze and critique the literature that we synthesized in our integrative review. Our results were created based on analysis of this Additional File.
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Nature volume 555 , pages 175–182 ( 2018 ) Cite this article
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Meta-analysis is the quantitative, scientific synthesis of research results. Since the term and modern approaches to research synthesis were first introduced in the 1970s, meta-analysis has had a revolutionary effect in many scientific fields, helping to establish evidence-based practice and to resolve seemingly contradictory research outcomes. At the same time, its implementation has engendered criticism and controversy, in some cases general and others specific to particular disciplines. Here we take the opportunity provided by the recent fortieth anniversary of meta-analysis to reflect on the accomplishments, limitations, recent advances and directions for future developments in the field of research synthesis.
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We dedicate this Review to the memory of Ingram Olkin and William Shadish, founding members of the Society for Research Synthesis Methodology who made tremendous contributions to the development of meta-analysis and research synthesis and to the supervision of generations of students. We thank L. Lagisz for help in preparing the figures. We are grateful to the Center for Open Science and the Laura and John Arnold Foundation for hosting and funding a workshop, which was the origination of this article. S.N. is supported by Australian Research Council Future Fellowship (FT130100268). J.G. acknowledges funding from the US National Science Foundation (ABI 1262402).
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Department of Ecology and Evolution, Stony Brook University, Stony Brook, 11794-5245, New York, USA
Jessica Gurevitch
School of Biological Sciences, Royal Holloway University of London, Egham, TW20 0EX, Surrey, UK
Julia Koricheva
Evolution and Ecology Research Centre and School of Biological, Earth and Environmental Sciences, University of New South Wales, Sydney, 2052, New South Wales, Australia
Shinichi Nakagawa
Diabetes and Metabolism Division, Garvan Institute of Medical Research, 384 Victoria Street, Darlinghurst, Sydney, 2010, New South Wales, Australia
School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, NE1 7RU, UK
Gavin Stewart
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All authors contributed equally in designing the study and writing the manuscript, and so are listed alphabetically.
Correspondence to Jessica Gurevitch , Julia Koricheva , Shinichi Nakagawa or Gavin Stewart .
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Reviewer Information Nature thanks D. Altman, M. Lajeunesse, D. Moher and G. Romero for their contribution to the peer review of this work.
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When combining another author’s ideas with your own, we have talked about how using the can help make sure your points are being adequately argued (if you have not read our handout on the evidence cycle, check it out!). Synthesis takes assertions (statements that describe your claim), evidence (facts and proof from outside sources), and commentary (your connections to why the evidence supports your claim), and blends these processes together to make a cohesive paragraph.
In other words, synthesis encompasses several aspects:
TIP: It’s a fruit smoothie!
Think of synthesis as a fruit smoothie that you are creating in your paper. You will have unique parts and flavors in your writing that you will need to blend together to make one tasty, unified drink!
Demonstrates how two or more sources agree with one another.
The collaborative nature of writing tutorials has been discussed by scholars like Andrea Lunsford (1991) and Stephen North (1984). In these essays, they explore the usefulness and the complexities of collaboration between tutors and students in writing center contexts.
Demonstrates how two or more sources support a main point in different ways.
While some scholars like Berlin (1987) have primarily placed their focus on the histories of large, famous universities, other scholars like Yahner and Murdick (1991) have found value in connecting their local histories to contrast or highlight trends found in bigger-name universities.
Demonstrates how one source builds on the idea of another.
Although North’s (1984) essay is fundamental to many writing centers today, Lunsford (1991) takes his ideas a step further by identifying different writing center models and also expanding North’s ideas on how writing centers can help students become better writers.
Demonstrates how one source discusses the effects of another source’s ideas.
While Healy (2001) notes the concerns of having primarily email appointments in writing centers, he also notes that constraints like funding, resources, and time affect how online resources are formed. For writing centers, email is the most economical and practical option for those wanting to offer online services but cannot dedicate the time or money to other online tutoring methods. As a result, in Neaderheiser and Wolfe’s (2009) reveals that of all the online options available in higher education, over 91% of institutions utilize online tutoring through email, meaning these constraints significantly affect the types of services writing centers offer.
To debate with clarity and precision, you may need to incorporate a quote into your statement. Using can help you to thoroughly introduce your quotes so that they fit in to your paragraph and your argument. Remember that you need to use the to bridge between your ideas and outside source material.
Berlin, J. (1987). Rhetoric and reality: Writing instruction in American colleges, 1900-1985 . Carbondale: Southern Illinois University Press.
Boquet, E.H. (2001). “Our little secret”: A history of writing centers, pre- to open admissions. In R.W. Barnett & J.S. Blumner (Eds.), The Allyn and Bacon guide to writing center theory and practice (pp. 42-60). Boston: Allyn and Bacon.
Carino, P. (1995). Early writing centers: Toward a history. The Writing Center Journal , 15 (2), 103-15.
Healy, D. (2001). From place to space: Perceptual and administrative issues in the online writing center. In R.W. Barnett & J.S. Blumner (Eds.), T he Allyn and Bacon guide to writing center theory and practice (pp. 541-554). Boston: Allyn and Bacon.
Lunsford, A. (1991). Collaboration, control, and the idea of the writing center. The Writing Center Journal , 12 (1), 310-75.
Neaderheiser, S. & Wolfe, J. (2009). Between technological endorsement and resistance: The state of online writing centers. The Writing Center Journal . 29 (1), 49-75.
North, S. (1984). The idea of a writing center. College English , 45 (5), 433-446.
Yahner, W. & Murdick, W. (1991). The evolution of a writing center: 1972-1990. Writing Center Journal , 11 (2), 13-28.
What are evidence syntheses.
According to the Royal Society, 'evidence synthesis' refers to the process of bringing together information from a range of sources and disciplines to inform debates and decisions on specific issues. They generally include a methodical and comprehensive literature synthesis focused on a well-formulated research question. Their aim is to identify and synthesize all of the scholarly research on a particular topic, including both published and unpublished studies. Evidence syntheses are conducted in an unbiased, reproducible way to provide evidence for practice and policy-making, as well as to identify gaps in the research. Evidence syntheses may also include a meta-analysis, a more quantitative process of synthesizing and visualizing data retrieved from various studies.
Evidence syntheses are much more time-intensive than traditional literature reviews and require a multi-person research team. See this PredicTER tool to get a sense of a systematic review timeline (one type of evidence synthesis). Before embarking on an evidence synthesis, it's important to clearly identify your reasons for conducting one. For a list of types of evidence synthesis projects, see the next tab.
How does a systematic review differ from a traditional literature review.
One commonly used form of evidence synthesis is a systematic review. This table compares a traditional literature review with a systematic review.
| ||
Review Question/Topic | Topics may be broad in scope; the goal of the review may be to place one's own research within the existing body of knowledge, or to gather information that supports a particular viewpoint. | Starts with a well-defined research question to be answered by the review. Reviews are conducted with the aim of finding all existing evidence in an unbiased, transparent, and reproducible way. |
Searching for Studies | Searches may be ad hoc and based on what the author is already familiar with. Searches are not exhaustive or fully comprehensive. | Attempts are made to find all existing published and unpublished literature on the research question. The process is well-documented and reported. |
Study Selection | Often lack clear reasons for why studies were included or excluded from the review. | Reasons for including or excluding studies are explicit and informed by the research question. |
Assessing the Quality of Included Studies | Often do not consider study quality or potential biases in study design. | Systematically assesses risk of bias of individual studies and overall quality of the evidence, including sources of heterogeneity between study results. |
Synthesis of Existing Research | Conclusions are more qualitative and may not be based on study quality. | Bases conclusion on quality of the studies and provide recommendations for practice or to address knowledge gaps. |
There are some reporting standards for evidence syntheses. These can serve as guidelines for protocol and manuscript preparation and journals may require that these standards are followed for the review type that is being employed (e.g. systematic review, scoping review, etc).
The PRISMA flow diagram depicts the flow of information through the different phases of an evidence synthesis. It maps the search (number of records identified), screening (number of records included and excluded), and selection (reasons for exclusion). Many evidence syntheses include a PRISMA flow diagram in the published manuscript.
See below for resources to help you generate your own PRISMA flow diagram.
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Published on July 4, 2022 by Eoghan Ryan . Revised on May 31, 2023.
Synthesizing sources involves combining the work of other scholars to provide new insights. It’s a way of integrating sources that helps situate your work in relation to existing research.
Synthesizing sources involves more than just summarizing . You must emphasize how each source contributes to current debates, highlighting points of (dis)agreement and putting the sources in conversation with each other.
You might synthesize sources in your literature review to give an overview of the field or throughout your research paper when you want to position your work in relation to existing research.
Example of synthesizing sources, how to synthesize sources, synthesis matrix, other interesting articles, frequently asked questions about synthesizing sources.
Let’s take a look at an example where sources are not properly synthesized, and then see what can be done to improve it.
This paragraph provides no context for the information and does not explain the relationships between the sources described. It also doesn’t analyze the sources or consider gaps in existing research.
Research on the barriers to second language acquisition has primarily focused on age-related difficulties. Building on Lenneberg’s (1967) theory of a critical period of language acquisition, Johnson and Newport (1988) tested Lenneberg’s idea in the context of second language acquisition. Their research seemed to confirm that young learners acquire a second language more easily than older learners. Recent research has considered other potential barriers to language acquisition. Schepens, van Hout, and van der Slik (2022) have revealed that the difficulties of learning a second language at an older age are compounded by dissimilarity between a learner’s first language and the language they aim to acquire. Further research needs to be carried out to determine whether the difficulty faced by adult monoglot speakers is also faced by adults who acquired a second language during the “critical period.”
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To synthesize sources, group them around a specific theme or point of contention.
As you read sources, ask:
Once you have a clear idea of how each source positions itself, put them in conversation with each other. Analyze and interpret their points of agreement and disagreement. This displays the relationships among sources and creates a sense of coherence.
Consider both implicit and explicit (dis)agreements. Whether one source specifically refutes another or just happens to come to different conclusions without specifically engaging with it, you can mention it in your synthesis either way.
Synthesize your sources using:
To more easily determine the similarities and dissimilarities among your sources, you can create a visual representation of their main ideas with a synthesis matrix . This is a tool that you can use when researching and writing your paper, not a part of the final text.
In a synthesis matrix, each column represents one source, and each row represents a common theme or idea among the sources. In the relevant rows, fill in a short summary of how the source treats each theme or topic.
This helps you to clearly see the commonalities or points of divergence among your sources. You can then synthesize these sources in your work by explaining their relationship.
Lenneberg (1967) | Johnson and Newport (1988) | Schepens, van Hout, and van der Slik (2022) | |
---|---|---|---|
Approach | Primarily theoretical, due to the ethical implications of delaying the age at which humans are exposed to language | Testing the English grammar proficiency of 46 native Korean or Chinese speakers who moved to the US between the ages of 3 and 39 (all participants had lived in the US for at least 3 years at the time of testing) | Analyzing the results of 56,024 adult immigrants to the Netherlands from 50 different language backgrounds |
Enabling factors in language acquisition | A critical period between early infancy and puberty after which language acquisition capabilities decline | A critical period (following Lenneberg) | General age effects (outside of a contested critical period), as well as the similarity between a learner’s first language and target language |
Barriers to language acquisition | Aging | Aging (following Lenneberg) | Aging as well as the dissimilarity between a learner’s first language and target language |
If you want to know more about ChatGPT, AI tools , citation , and plagiarism , make sure to check out some of our other articles with explanations and examples.
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Synthesizing sources means comparing and contrasting the work of other scholars to provide new insights.
It involves analyzing and interpreting the points of agreement and disagreement among sources.
You might synthesize sources in your literature review to give an overview of the field of research or throughout your paper when you want to contribute something new to existing research.
A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .
It is often written as part of a thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.
Topic sentences help keep your writing focused and guide the reader through your argument.
In an essay or paper , each paragraph should focus on a single idea. By stating the main idea in the topic sentence, you clarify what the paragraph is about for both yourself and your reader.
At college level, you must properly cite your sources in all essays , research papers , and other academic texts (except exams and in-class exercises).
Add a citation whenever you quote , paraphrase , or summarize information or ideas from a source. You should also give full source details in a bibliography or reference list at the end of your text.
The exact format of your citations depends on which citation style you are instructed to use. The most common styles are APA , MLA , and Chicago .
If you want to cite this source, you can copy and paste the citation or click the “Cite this Scribbr article” button to automatically add the citation to our free Citation Generator.
Ryan, E. (2023, May 31). Synthesizing Sources | Examples & Synthesis Matrix. Scribbr. Retrieved September 2, 2024, from https://www.scribbr.com/working-with-sources/synthesizing-sources/
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October 3, 2013 workshop.
View workshop video . Download final program . View agenda, download papers, and find journal articles .
Read related articles in Risk Analysis , including the workshop summary and introduction to the series.*
Methods for research synthesis, including systematic review, meta-analysis, and expert elicitation, are used in almost every field to combine the results of studies that address similar quantities or phenomena. These methods are often employed when estimating parameter values for policy analysis, such as the toxicity of a substance, the monetary value of risk reductions, or the effectiveness of different interventions. However, researchers often face difficult questions about how to choose among these methods and how to adapt each method to particular problems and available data. If used inappropriately, these approaches may yield misleading conclusions about the relative merits of alternative interventions, leading to undesirable policy outcomes.
This Harvard Center for Risk Analysis workshop is part of an interdisciplinary project to improve the use of these methods in policy analysis. Its goal is to promote evidence-based decision making. Its objectives include:
The workshop provides an opportunity for presentation and discussion of invited papers on the application of these methods in diverse contexts. Papers evaluate, for example, how a particular method should be applied in different contexts, or how different methods should be used for a particular application.
Major funding for this project is provided by the National Science Foundation , with additional support from the Harvard Superfund Research Program Research Translation Core, the Harvard University Center for the Environment , the European Association of Environmental and Resource Economists , Gradient , the Health Effects Institute , the Texas Commission on Environmental Quality , the Society for Risk Analysis Economics and Benefits Analysis Specialty Group , and the U.S. Department of Agriculture Economics Research Service .
* We thank Wiley and the Risk Analysis editors for providing temporary free access to the introduction to the series.
How To Synthesise The Existing Research (With Examples)
By: Derek Jansen (MBA) | Expert Reviewer: Eunice Rautenbach (DTech) | August 2023
One of the most common mistakes that students make when writing a literature review is that they err on the side of describing the existing literature rather than providing a critical synthesis of it. In this post, we’ll unpack what exactly synthesis means and show you how to craft a strong literature synthesis using practical examples.
This post is based on our popular online course, Literature Review Bootcamp . In the course, we walk you through the full process of developing a literature review, step by step. If it’s your first time writing a literature review, you definitely want to use this link to get 50% off the course (limited-time offer).
As a starting point, let’s quickly define what exactly we mean when we use the term “synthesis” within the context of a literature review.
Simply put, literature synthesis means going beyond just describing what everyone has said and found. Instead, synthesis is about bringing together all the information from various sources to present a cohesive assessment of the current state of knowledge in relation to your study’s research aims and questions .
Put another way, a good synthesis tells the reader exactly where the current research is “at” in terms of the topic you’re interested in – specifically, what’s known , what’s not , and where there’s a need for more research .
So, how do you go about doing this?
Well, there’s no “one right way” when it comes to literature synthesis, but we’ve found that it’s particularly useful to ask yourself five key questions when you’re working on your literature review. Having done so, you can then address them more articulately within your actual write up. So, let’s take a look at each of these questions.
The first question that you need to ask yourself is: “Overall, what things seem to be agreed upon by the vast majority of the literature?”
For example, if your research aim is to identify which factors contribute toward job satisfaction, you’ll need to identify which factors are broadly agreed upon and “settled” within the literature. Naturally, there may at times be some lone contrarian that has a radical viewpoint , but, provided that the vast majority of researchers are in agreement, you can put these random outliers to the side. That is, of course, unless your research aims to explore a contrarian viewpoint and there’s a clear justification for doing so.
Identifying what’s broadly agreed upon is an essential starting point for synthesising the literature, because you generally don’t want (or need) to reinvent the wheel or run down a road investigating something that is already well established . So, addressing this question first lays a foundation of “settled” knowledge.
Related to the previous point, but on the other end of the spectrum, is the equally important question: “Where do the disagreements lie?” .
In other words, which things are not well agreed upon by current researchers? It’s important to clarify here that by disagreement, we don’t mean that researchers are (necessarily) fighting over it – just that there are relatively mixed findings within the empirical research , with no firm consensus amongst researchers.
This is a really important question to address as these “disagreements” will often set the stage for the research gap(s). In other words, they provide clues regarding potential opportunities for further research, which your study can then (hopefully) contribute toward filling. If you’re not familiar with the concept of a research gap, be sure to check out our explainer video covering exactly that .
The next question you need to ask yourself is: “Which key theories seem to be coming up repeatedly?” .
Within most research spaces, you’ll find that you keep running into a handful of key theories that are referred to over and over again. Apart from identifying these theories, you’ll also need to think about how they’re connected to each other. Specifically, you need to ask yourself:
Simply put, you’ll need to pay careful attention to the key theories in your research area, as they will need to feature within your theoretical framework , which will form a critical component within your final literature review. This will set the foundation for your entire study, so it’s essential that you be critical in this area of your literature synthesis.
If this sounds a bit fluffy, don’t worry. We deep dive into the theoretical framework (as well as the conceptual framework) and look at practical examples in Literature Review Bootcamp . If you’d like to learn more, take advantage of our limited-time offer to get 60% off the standard price.
The next question that you need to address in your literature synthesis is an important one, and that is: “Which contexts have (and have not) been covered by the existing research?” .
For example, sticking with our earlier hypothetical topic (factors that impact job satisfaction), you may find that most of the research has focused on white-collar , management-level staff within a primarily Western context, but little has been done on blue-collar workers in an Eastern context. Given the significant socio-cultural differences between these two groups, this is an important observation, as it could present a contextual research gap .
In practical terms, this means that you’ll need to carefully assess the context of each piece of literature that you’re engaging with, especially the empirical research (i.e., studies that have collected and analysed real-world data). Ideally, you should keep notes regarding the context of each study in some sort of catalogue or sheet, so that you can easily make sense of this before you start the writing phase. If you’d like, our free literature catalogue worksheet is a great tool for this task.
Last but certainly not least, you need to ask yourself the question: “What types of research methodologies have (and haven’t) been used?”
For example, you might find that most studies have approached the topic using qualitative methods such as interviews and thematic analysis. Alternatively, you might find that most studies have used quantitative methods such as online surveys and statistical analysis.
But why does this matter?
Well, it can run in one of two potential directions . If you find that the vast majority of studies use a specific methodological approach, this could provide you with a firm foundation on which to base your own study’s methodology . In other words, you can use the methodologies of similar studies to inform (and justify) your own study’s research design .
On the other hand, you might argue that the lack of diverse methodological approaches presents a research gap , and therefore your study could contribute toward filling that gap by taking a different approach. For example, taking a qualitative approach to a research area that is typically approached quantitatively. Of course, if you’re going to go against the methodological grain, you’ll need to provide a strong justification for why your proposed approach makes sense. Nevertheless, it is something worth at least considering.
Regardless of which route you opt for, you need to pay careful attention to the methodologies used in the relevant studies and provide at least some discussion about this in your write-up. Again, it’s useful to keep track of this on some sort of spreadsheet or catalogue as you digest each article, so consider grabbing a copy of our free literature catalogue if you don’t have anything in place.
Alright, so we’ve looked at five important questions that you need to ask (and answer) to help you develop a strong synthesis within your literature review. To recap, these are:
Importantly, you’re not just asking yourself these questions for the sake of asking them – they’re not just a reflection exercise. You need to weave your answers to them into your actual literature review when you write it up. How exactly you do this will vary from project to project depending on the structure you opt for, but you’ll still need to address them within your literature review, whichever route you go.
The best approach is to spend some time actually writing out your answers to these questions, as opposed to just thinking about them in your head. Putting your thoughts onto paper really helps you flesh out your thinking . As you do this, don’t just write down the answers – instead, think about what they mean in terms of the research gap you’ll present , as well as the methodological approach you’ll take . Your literature synthesis needs to lay the groundwork for these two things, so it’s essential that you link all of it together in your mind, and of course, on paper.
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Systematic reviews & evidence synthesis methods.
According to the Royal Society, 'evidence synthesis' refers to the process of bringing together information from a range of sources and disciplines to inform debates and decisions on specific issues. They generally include a methodical and comprehensive literature synthesis focused on a well-formulated research question. Their aim is to identify and synthesize all of the scholarly research on a particular topic, including both published and unpublished studies. Evidence syntheses are conducted in an unbiased, reproducible way to provide evidence for practice and policy-making, as well as to identify gaps in the research. Evidence syntheses may also include a meta-analysis, a more quantitative process of synthesizing and visualizing data retrieved from various studies.
Evidence syntheses are much more time-intensive than traditional literature reviews and require a multi-person research team. See this PredicTER tool to get a sense of a systematic review timeline (one type of evidence synthesis). Before embarking on an evidence synthesis, it's important to clearly identify your reasons for conducting one. For a list of types of evidence synthesis projects, see the Types of Evidence Synthesis tab.
One commonly used form of evidence synthesis is a systematic review. This table compares a traditional literature review with a systematic review.
| ||
Review Question/Topic | Topics may be broad in scope; the goal of the review may be to place one's own research within the existing body of knowledge, or to gather information that supports a particular viewpoint. | Starts with a well-defined research question to be answered by the review. Reviews are conducted with the aim of finding all existing evidence in an unbiased, transparent, and reproducible way. |
Searching for Studies | Searches may be ad hoc and based on what the author is already familiar with. Searches are not exhaustive or fully comprehensive. | Attempts are made to find all existing published and unpublished literature on the research question. The process is well-documented and reported. |
Study Selection | Often lack clear reasons for why studies were included or excluded from the review. | Reasons for including or excluding studies are explicit and informed by the research question. |
Assessing the Quality of Included Studies | Often do not consider study quality or potential biases in study design. | Systematically assesses risk of bias of individual studies and overall quality of the evidence, including sources of heterogeneity between study results. |
Synthesis of Existing Research | Conclusions are more qualitative and may not be based on study quality. | Bases conclusion on quality of the studies and provide recommendations for practice or to address knowledge gaps. |
There are some reporting standards for evidence syntheses. These can serve as guidelines for protocol and manuscript preparation and journals may require that these standards are followed for the review type that is being employed (e.g. systematic review, scoping review, etc).
The PRISMA flow diagram depicts the flow of information through the different phases of an evidence synthesis. It maps the search (number of records identified), screening (number of records included and excluded), and selection (reasons for exclusion). Many evidence syntheses include a PRISMA flow diagram in the published manuscript.
See below for resources to help you generate your own PRISMA flow diagram.
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When you look for areas where your sources agree or disagree and try to draw broader conclusions about your topic based on what your sources say, you are engaging in synthesis. Writing a research paper usually requires synthesizing the available sources in order to provide new insight or a different perspective into your particular topic (as opposed to simply restating what each individual source says about your research topic).
Note that synthesizing is not the same as summarizing.
There are two types of syntheses: explanatory syntheses and argumentative syntheses . Explanatory syntheses seek to bring sources together to explain a perspective and the reasoning behind it. Argumentative syntheses seek to bring sources together to make an argument. Both types of synthesis involve looking for relationships between sources and drawing conclusions.
In order to successfully synthesize your sources, you might begin by grouping your sources by topic and looking for connections. For example, if you were researching the pros and cons of encouraging healthy eating in children, you would want to separate your sources to find which ones agree with each other and which ones disagree.
After you have a good idea of what your sources are saying, you want to construct your body paragraphs in a way that acknowledges different sources and highlights where you can draw new conclusions.
As you continue synthesizing, here are a few points to remember:
Below are two examples of synthesis: one where synthesis is NOT utilized well, and one where it is.
Parents are always trying to find ways to encourage healthy eating in their children. Elena Pearl Ben-Joseph, a doctor and writer for KidsHealth , encourages parents to be role models for their children by not dieting or vocalizing concerns about their body image. The first popular diet began in 1863. William Banting named it the “Banting” diet after himself, and it consisted of eating fruits, vegetables, meat, and dry wine. Despite the fact that dieting has been around for over a hundred and fifty years, parents should not diet because it hinders children’s understanding of healthy eating.
In this sample paragraph, the paragraph begins with one idea then drastically shifts to another. Rather than comparing the sources, the author simply describes their content. This leads the paragraph to veer in an different direction at the end, and it prevents the paragraph from expressing any strong arguments or conclusions.
An example of a stronger synthesis can be found below.
Parents are always trying to find ways to encourage healthy eating in their children. Different scientists and educators have different strategies for promoting a well-rounded diet while still encouraging body positivity in children. David R. Just and Joseph Price suggest in their article “Using Incentives to Encourage Healthy Eating in Children” that children are more likely to eat fruits and vegetables if they are given a reward (855-856). Similarly, Elena Pearl Ben-Joseph, a doctor and writer for Kids Health , encourages parents to be role models for their children. She states that “parents who are always dieting or complaining about their bodies may foster these same negative feelings in their kids. Try to keep a positive approach about food” (Ben-Joseph). Martha J. Nepper and Weiwen Chai support Ben-Joseph’s suggestions in their article “Parents’ Barriers and Strategies to Promote Healthy Eating among School-age Children.” Nepper and Chai note, “Parents felt that patience, consistency, educating themselves on proper nutrition, and having more healthy foods available in the home were important strategies when developing healthy eating habits for their children.” By following some of these ideas, parents can help their children develop healthy eating habits while still maintaining body positivity.
In this example, the author puts different sources in conversation with one another. Rather than simply describing the content of the sources in order, the author uses transitions (like "similarly") and makes the relationship between the sources evident.
Synthesis matrix example.
What is synthesis? | What synthesis is NOT: |
---|---|
You can sort the literature in various ways, for example:
Read your sources carefully and find the main idea(s) of each source
Look for similarities in your sources – which sources are talking about the same main ideas? (for example, sources that discuss the historical background on your topic)
Use the worksheet (above) or synthesis matrix (below) to get organized
This work can be messy. Don't worry if you have to go through a few iterations of the worksheet or matrix as you work on your lit review!
In the four examples below, only ONE shows a good example of synthesis: the fourth column, or Student D . For a web accessible version, click the link below the image.
Long description of "Four Examples of Student Writing" for web accessibility
Click on the example to view the pdf.
From Jennifer Lim
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First, let's be perfectly clear about what synthesizing your research isn't :
When you synthesize your research, your job is to help your reader understand the current state of the conversation on your topic, relative to your research question. That may include doing the following:
Essentially, you're telling your reader where they are (and where you are) in the scholarly conversation about your project.
Synthesis, step by step.
This is what you need to do before you write your review.
Published by Olive Robin at October 17th, 2023 , Revised On October 17, 2023
The ability to effectively incorporate multiple sources into one’s work is not just a skill, but a necessity. Whether we are talking about research papers, articles, or even simple blog posts, synthesising sources can elevate our content to a more nuanced, comprehensive, and insightful level. But what does it truly mean to synthesise sources, and how does it differ from the commonly understood techniques of summarising and paraphrasing?
When finding sources , it is imperative to distinguish between various available information types. Secondary sources , for example, provide interpretations and analyses based on primary sources. Synthesising goes beyond the mere gathering of information. It involves the complex task of interweaving multiple sources to generate a broader and richer perspective. When we synthesise, we are not just collecting; we are connecting.
By merging various viewpoints and data, we provide our readers with a well-rounded understanding of the topic. This approach ensures that our work is grounded in credible sources while also adding unique insights.
At first glance, these three techniques might seem similar, but they serve distinctly different purposes:
Synthesis is the art of blending multiple sources to create a unified narrative or argument. It is essential to use signal phrases to introduce these sources naturally, helping the reader follow the information flow. Block quotes can also be used for direct quotations, especially if they’re longer.
Here, we restate the original content using different words. While the wording changes, the essence and core meaning remain intact. This method is useful for clarifying complex ideas or for tailoring content to a specific audience.
Synthesis is the art of blending multiple sources to create a unified narrative or argument. It is not about echoing what others have said; it is about drawing connections, identifying patterns, and building a cohesive piece that holds its own merit.
Synthesising sources is a method used in research and writing wherein the author combines, interprets, and analyses information from various sources to generate a unified perspective, narrative, or argument. It involves a process that we can call source evaluation . It is an intricate process that goes beyond simply collecting data or quoting authors. Instead, it involves evaluating, integrating, and constructing a new narrative based on a collective understanding of all the sources under consideration.
Imagine a quilt where each piece of fabric represents a different source. Synthesising would be the act of sewing these individual pieces together in such a way that they form a beautiful, cohesive blanket. Each piece retains its uniqueness but contributes to the larger design and purpose of the quilt.
The art of synthesis, while a nuanced aspect of research and writing, holds unparalleled significance in constructing meaningful, in-depth content. Here is a detailed exploration of why synthesis is pivotal:
Here is a step-by-step guide on how to synthesise sources.
Before you can synthesise sources effectively, you must first understand them individually. A strong synthesis is built upon a clear understanding of each source’s content, context, and nuances.
Sources will often touch upon similar themes, even if they approach them differently. Recognising these themes can act as a foundation for synthesis.
Different sources might have diverging opinions or findings. Recognising these differences is crucial to produce a balanced synthesis.
Not all sources will hold equal weight or relevance in your synthesis.
A clear structure is essential to guide your readers through the synthesised narrative.
This step involves the actual writing, where you combine the insights, evidence, and analysis into a singular narrative.
Always credit original authors and sources to maintain integrity in your work and avoid plagiarism. Knowing how to cite sources is crucial in this process.
There are multiple citation styles (e.g., APA, MLA, Chicago), and your choice will often depend on your discipline or the preference of your institution or publication.
Citation Tools: Consider using tools like Zotero, Mendeley, or EndNote to help streamline and manage your citations.
Let’s explore some examples of synthesising sources.
Scenario: You have sources that discuss the causes of climate change. Some sources argue for anthropogenic (human-caused) factors, while others emphasise natural cycles.
Scenario: You are examining the Battle of Waterloo from British, French, and Prussian primary sources.
Scenario: You are researching the effects of remote learning on student performance and well-being during the pandemic.
These are the different tools that can be used for synthesising sources.
Managing references can be cumbersome, especially when dealing with numerous sources. Citation tools can help organise, format, and insert citations with ease.
Mind mapping helps visually organise and interlink ideas, making the synthesis process more intuitive.
Effective note-taking is fundamental to understanding and organising information from various sources. Digital note-taking apps often offer features like tagging, search functionalities, and integration with other tools.
What is a literature review.
A literature review is a comprehensive survey of existing research on a particular topic, synthesising findings to provide an overview of key concepts, debates, and gaps in knowledge. It establishes a foundation for new research, highlighting relevant studies and contextualising them within the broader academic conversation.
To synthesise a source, thoroughly understand its content, and then integrate its insights with information from other sources. This involves comparing and contrasting viewpoints, identifying patterns, and constructing a cohesive narrative or argument that offers a broader perspective rather than merely echoing the original source’s content.
Citing sources acknowledges original authors, maintains academic integrity, and provides readers with a reference for verification. It prevents plagiarism by giving credit to the ideas and research of others, allowing readers to trace the evolution of thought and confirm the reliability and accuracy of the presented information.
Topic sentences are the main statements that introduce and summarise a paragraph’s main idea or focus. They provide context and direction, helping readers follow the writer’s argument or narrative. Typically placed at the beginning of a paragraph, they act as signposts, guiding the flow of the discussion.
The CRAAP Test is an acronym used as a checklist to help individuals evaluate the credibility and relevance of sources, especially in academic or research contexts. CRAAP stands for Currency, Relevance, Authority, Accuracy, and Purpose. Each of these criteria can help a researcher determine if a source is trustworthy and suitable for their needs.
A tertiary source is an information source that compiles, analyses, and synthesises both primary and secondary sources.
When researching or exploring a new topic, the distinction between primary and secondary sources is paramount. The validity, reliability, and relevance of the information you gather will heavily depend on the type of source you consult.
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Meta-analysis and integrative data analysis are research synthesis methods that aim to provide large-scale evidence by pooling data from multiple independently conducted studies.
Clarke, N., Kim, S.-Y., White, H. R., Jiao, Y., & Mun, E.-Y. (2013). Associations between alcohol
use and alcohol-related negative consequences among Black and White college men and women. Journal of Studies on Alcohol and Drugs, 74 (4), 521-531.
Huh, D., Mun, E.-Y., Larimer, M. White, H. R., Ray, A. E., Rhew, I., Kim, S.-Y., Jiao, Y., & Atkins, D. C. (2015). Brief motivational interventions for college student drinking may not be as powerful as we think: An individual participant-level data meta-analysis. Alcoholism: Clinical and Experimental Research, 39 (5), 919-931.
Huh, D., Mun, E. Y., Walters, S. T., Zhou, Z., & Atkins, D. C. (2019). A tutorial on individual participant data meta-analysis using Bayesian multilevel modeling to estimate alcohol intervention effects across heterogeneous studies. Addictive behaviors , 94 , 162-170.
Huh, D., Li, X., Zhou, Z., Walters, S. T., Baldwin, S. A., Tan, Z., … & Mun, E. Y. (2022). A structural equation modeling approach to meta-analytic mediation analysis using individual participant data: Testing protective behavioral strategies as a mediator of brief motivational intervention effects on alcohol-related problems. Prevention Science , 23 (3), 390-402.
Jiao, Y., Mun, E.-Y., Trikalinos, T., & Xie, M. (2020). A CD-based mapping method for combining multiple related parameters from heterogeneous intervention trials. Statistics and Its Interface, 13 (4), 533-549.
Mun, E. Y., Li, X., Lineberry, S., Tan, Z., Huh, D., Walters, S. T., … & Project INTEGRATE Team. (2022). Do brief alcohol interventions reduce driving after drinking among college students? A two-step meta-analysis of individual participant data. Alcohol and Alcoholism , 57 (1), 125-135.
Mun, E.-Y., & Ray, A. E. (2018). Integrative data analysis from a unifying research synthesis perspective. In H. E. Fitzgerald & L. I. Puttler (Eds.), Alcohol use disorders: A developmental science approach to etiology (pp. 341-353). New York: Oxford University Press.
Mun, E.-Y., Atkins, D. C., & Walters, S. T. (2015). Is motivational interviewing effective at reducing alcohol misuse in young adults? A critical review of Foxcroft et al. (2014). Psychology of Addictive Behaviors, 29 (4), 836-846.
Mun, E.-Y., de la Torre, J., Atkins, D. C., White, H. R., Ray, A. E., Kim, S.-Y., Jiao, Y., Clarke, N., Huo, Y., Larimer, M. E., Huh, D., & The Project INTEGRATE Team (2015). Project INTEGRATE: An integrative study of brief alcohol interventions for college students. Psychology of Addictive Behaviors, 29 (1), 34-48.
Mun, E.-Y., Jiao, Y., & Xie, M. (2016). Integrative data analysis for research in developmental
psychopathology. In D. Cicchetti (Ed.), Developmental psychopathology (3rd ed., Vol. 1, pp. 1042-1087). New York: Wiley.
Mun, E.-Y., Zhou, Z., Huh, D., Tan, L., Li, D., Tanner-Smith, E. E., Walters, S. T., & Larimer, M. E. (2022). Brief alcohol interventions are effective through six months: Findings from marginalized zero-inated Poisson and negative binomial models in a two-step IPD meta-analysis. Prevention Science . https://doi.org/10.1007/s11121-022-01420-1
White, H. R., Jiao, Y., Ray, A. E., Huh, D., Atkins, D. C., Larimer, M. E.,… Mun, E.-Y. (2015). Are there secondary effects on marijuana use from brief alcohol interventions for college students? Journal of Studies on Alcohol and Drugs, 76 (3), 367-377.
White, H. R., Anderson, K., Ray, A. E., & Mun, E.-Y. (2016). Do drinking motives distinguish extreme drinking college students from their peers? Addictive Behaviors, 60 , 213-218.
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Background: Physiotherapy and chronic low back pain (CLBP) form a broad and quickly developing research area. The aim of this article was to holistically, thematically and chronologically analyze and synthesize the literature production in this research area and identify the most prolific research entities and research themes.
Methods: This article quantitatively and qualitatively analyzed research literature production harvested from the Scopus bibliometric database, using a triangulation of bibliometric and thematic analysis. For this, Excel 2024, Bibliometrix Biblioshiny 4.1 and VOSviewer version 1.6.20 softwares were used.
Results: In the Scopus database, 2843 data sources were found, which were published between 1974 and 26 February 2024. The growth trend has been linearly positive since the beginning of publication, and after 2018 exponential growth began. A review of the most prolific entities showed that the most literature was published in America, Europe and Australasia. The thematic analysis of the information sources identified six main themes (pathophysiology of CLBP and the quantification assessment tools, diagnostics and CLBP treatment, CLBP questionnaires and surveys, quality of life, complementary methods in physiotherapy and psychosocioeconomic aspects), while the chronological analysis revealed three main areas of development: assessment tools, CLBP processing and study methodology.
Conclusions: The results of this bibliometric study present a good starting point for further research, providing taxonomy and research landscapes as a holistic framework offering multidisciplinary knowledge about CLBP, while chronological analysis provides a basis for identifying prospective research trends. This article offers an interdisciplinary view of the current issue of public health. The results of this study provide a basis for the development of both the physiotherapy and epidemiological fields.
Keywords: bibliometric analysis; chronic low back pain; knowledge synthesis; physiotherapy.
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The authors declare no conflicts of interest.
The dynamics of research literature…
The dynamics of research literature production.
The dynamics of research literature production after 2018.
The bibliometric map of the…
The bibliometric map of the research on the use of physiotherapy in CLBP.
Chronological diagram of the research…
Chronological diagram of the research topics.
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29 August 2024
The straightforward and effective method was developed at the Flow Chemistry group at the Van ‘t Hoff Institute for Molecular Sciences led by Prof. Timothy Noël, in cooperation with researchers in Italy, Spain and the UK, both from academia and industry. Applying the principles of flow chemistry, where reactions take place in closed systems of small tubes, makes for safe and controlled chemistry. It also offers greater versatility and flexibility over more common procedures using traditional chemical glassware.
Many pharmaceutical compounds (such as anti-depressants) as well as agrochemical compounds (such as pesticides) benefit from the presence of a trifluoromethyl (-CF 3 ) group. It enhances hydrophobicity and increases metabolic stability, thus improving efficacy and lowering the required dose or concentration.
To introduce the fluorine atoms in these molecules, their synthesis often requires bespoke fluorinated reagents. Many of these are among the family of PFAS compounds and thus will face future legislation. The synthesis protocol now presented in the Science paper provides a viable alternative since it only requires caesium fluoride salt as the fluorine source. Such PFAS-free synthesis of fluorinated agents can provide an environmentally more friendly option for the synthesis of pharmaceutical compounds, which motivated scientists from AstraZeneca to participate in the research.
In addition, the new synthesis protocol enables coupling of the CF 3 group through a sulphur (S), nitrogen (N) or oxygen (O) atom. Such fluorinated motifs confer unique features to drug molecules and agrochemicals, impacting their lipophilicity, oxidation resistance, and acid-base properties.
The Science paper presents a versatile microfluidic flow module for generating reactive N–, S– and O–CF 3 anions. These are prepared in a packed bed flow reactor containing the caesium fluoride salt. Appropriate (S, O or N containing) precursors are then led through this reactor.
There, they are fluorinated with high efficiency due to the high surface area of the salt in the packed bed as well and the improved mixing of the organic intermediates. Importantly, this approach also offers enhanced safety as all formed intermediates are contained within the microfluidic system.
Another important feature of the flow system described in Science is the integration of the anion generating module with a downstream reaction module. There, the N–, S– or O–CF 3 anions react with appropriate substrates to achieve pharmaceutical and agrochemical active ingredients as the desired end products.
In combination, the anion generator module and the downstream reactor provide a streamlined platform for the derivatization of molecules bearing N–, S– and O–CF 3 motifs. This innovative approach is poised to impact the development of new pharmaceutical drugs by enhancing their properties while improving safety and sustainability in their production processes. In their Science paper, the researchers report the combination of various anions with a range of substrates, resulting in multiple fluorinated products with relevance to pharmaceutical and agrochemical syntheses. In many cases the research team was able to report very satisfactory yields. Moreover, the operational parameters (e.g. reaction times) offer a good prospect for actual implementation in an academic as well as an industrial context.
Mauro Spennacchio, Miguel Bernús, Jelena Stanić, Daniele Mazzarella, Marco Colella, James J. Douglas, Omar Boutureira, Timothy Noël: A unified flow strategy for the preparation and use of trifluoromethyl-heteroatom anions. Science, 385, 6712, p991-996 DOI: 10.1126/science.adq2954
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IMAGES
VIDEO
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Learn how to combine the ideas and findings of multiple sources to make an overall point in a literature review or essay. Follow four steps: organize your sources, outline your structure, write paragraphs with topic sentences, and revise, edit and proofread.
Learn about the process of combining the results of multiple primary research studies to test the same conceptual hypothesis. Find out the techniques and methods of quantitative and qualitative research synthesis, such as meta-analysis and narrative synthesis.
1. Introduction. Research or scientific synthesis is the integration and assessment of knowledge and research findings pertinent to a particular issue with the aim of increasing the generality and applicability of, and access to, those findings (Hampton & Parker 2011, Magliocca et al., 2014, Baron et al. 2017).Synthesis of existing research and case studies can also generate new knowledge.
Research synthesis is the overarching term we use to describe approaches to combining, aggregating, integrating, and synthesizing primary research findings. Each synthesis methodology draws on different types of findings depending on the purpose and product of the chosen synthesis (see Additional File 1). 3.
Meta-analysis is the quantitative, scientific synthesis of research results. Since the term and modern approaches to research synthesis were first introduced in the 1970s, meta-analysis has had a ...
In other words, synthesis encompasses several aspects: It is the process of integrating support from more than one source for one idea/argument while also identifying how sources are related to each other and to your main idea. It is an acknowledgment of how the source material from several sources address the same question/research topic.
Research Synthesis Methods, the official journal of the Society for Research Synthesis Methodology, is a multidisciplinary peer reviewed journal devoted to the development and dissemination of methods for designing, conducting, analyzing, interpreting, reporting, and applying systematic research synthesis.It aims to facilitate the creation and exchange of knowledge about research synthesis ...
The Handbook of Research Synthesis and Meta-Analysis incorporates state-of-the-art techniques from all quantitative synthesis traditions. Distilling a vast technical literature and many informal sources, the Handbook provides a portfolio of the most effective solutions to the problems of quantitative data integration.
Qualitative research synthesis is a diverse set of methods for combining the data or the results of multiple studies on a topic to generate new knowledge, theory and applications. Use of qualitative research synthesis is rapidly expanding across disciplines. Aggregative and interpretive models of qualitative research synthesis are defined and ...
Their aim is to identify and synthesize all of the scholarly research on a particular topic, including both published and unpublished studies. Evidence syntheses are conducted in an unbiased, reproducible way to provide evidence for practice and policy-making, as well as to identify gaps in the research. Evidence syntheses may also include a ...
Learn how to synthesize sources by combining and analyzing them to provide new insights. See examples of effective and poor synthesis, and use a synthesis matrix to organize your sources.
The Fifth Edition of Harris Cooper's bestselling text offers practical advice on how to conduct a synthesis of research in the social, behavioral, and health sciences. The book is written in plain language with four running examples drawn from psychology, education, and health science. With ample coverage of literature searching and the ...
A comprehensive guide to conducting research syntheses and meta-analyses in the social and behavioral sciences. Learn from leading experts how to formulate problems, search and evaluate literature, statistically integrate data, and report results.
Learn about methods for research synthesis, such as systematic review, meta-analysis, and expert elicitation, and how they are used in policy analysis. This project aims to improve the use of these methods across disciplines and to promote evidence-based decision making.
In this post, we'll unpack what exactly synthesis means and show you how to craft a strong literature synthesis using practical examples. This post is based on our popular online course, Literature Review Bootcamp. In the course, we walk you through the full process of developing a literature review, step by step.
According to the Royal Society, 'evidence synthesis' refers to the process of bringing together information from a range of sources and disciplines to inform debates and decisions on specific issues. They generally include a methodical and comprehensive literature synthesis focused on a well-formulated research question.
There are two types of syntheses: explanatory syntheses and argumentative syntheses. Explanatory syntheses seek to bring sources together to explain a perspective and the reasoning behind it. Argumentative syntheses seek to bring sources together to make an argument. Both types of synthesis involve looking for relationships between sources and ...
The Handbook of Research Synthesis is an attempt to bring together in a single volume state-of-the-art descriptions of every phase of the research synthesis process, from problem formulation to report writing. Determining the content of the Handbook required us to use multiple decision criteria.
Describing how sources converse each other. Organizing similar ideas together so readers can understand how they overlap. Synthesis helps readers see where you add your own new ideas to existing knowledge. Critiquing a source. Simply comparing and contrasting sources. A series of summaries. Direct quotes without using your own voice.
Synthesis, step by step. This is what you need to do before you write your review.. Identify and clearly describe your research question (you may find the Formulating PICOT Questions table at the Additional Resources tab helpful).; Collect sources relevant to your research question.
Thematic synthesis is an interpretative approach to reviewing based on the methods of thematic analysis used in primary research. Thematic synthesis methods however go further than thematic analysis methods and enable new insights, interpretations and theory to be developed not seen in individual primary studies. It is a frequently used method ...
Example 3: Synthesising Qualitative And Quantitative Research On A Social Issue. Scenario: You are researching the effects of remote learning on student performance and well-being during the pandemic. Synthesis Approach. Start with an introduction to the sudden shift to remote learning due to COVID-19.
Meta-analysis and integrative data analysis are research synthesis methods that aim to provide large-scale evidence by pooling data from multiple independently conducted studies. Dr. Eun-Young Mun Dr. Zhengyang Zhou Clarke, N., Kim, S.-Y., White, H. R., Jiao, Y., & Mun, E.-Y. (2013). Associations between alcohol use and alcohol-related negative ...
This video walks you through how to engage in synthesis in order to take research from multiple sources, your own arguments and turn it into a research paper...
Background: Physiotherapy and chronic low back pain (CLBP) form a broad and quickly developing research area. The aim of this article was to holistically, thematically and chronologically analyze and synthesize the literature production in this research area and identify the most prolific research entities and research themes.
The synthesis protocol now presented in the Science paper provides a viable alternative since it only requires caesium fluoride salt as the fluorine source. Such PFAS-free synthesis of fluorinated agents can provide an environmentally more friendly option for the synthesis of pharmaceutical compounds, which motivated scientists from AstraZeneca ...
His research interests focus on total synthesis of bioactive natural products and pharmaceuticals. Professor Pei Tang received his B.S. degree in 2005, and his Ph.D. degree in 2011 under the supervision of Prof. Feng-Peng Wang at Sichuan University. From 2012 to 2014, he was a postdoctoral researcher in Prof. Yong Qin's group at Chongqing ...
Make your next market research presentation a breeze with this sleek and professional template. Features of this template . 20 ready-to-use 16:9 slides completely customizable to suit your needs; Hundreds of charts, frames, lines and shapes to choose from; Handy animation and transition features for each slides;
Sep. 20, 2022 — Research into the synthesis of new materials could lead to more sustainable and environmentally friendly items such as solar panels and light emitting diodes (LEDs). Scientists ...
Objective:There are significant temporal and financial barriers for individuals with personality disorders (PD) receiving evidence-based psychological treatments. Emerging research indicates Group Schema Therapy (GST) may be an accessible, efficient, and cost-effective PD intervention, however, there has been no synthesis of the available evidence to date. This review therefore aimed to ...