Synthesizing Quantitative Evidence

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Many synthesis methods are new or emerging and several were not explicitly developed for combining different types of evidence. Nonetheless there are some approaches to synthesis which appear to offer potential for integrating qualitative and quantitative research evidence and we categorise these in four broad groups, as narrative, qualitative, quantitative or Bayesian approaches.

Narrative approaches Narrative synthesis seeks to move beyond a summary of the research literature to generate new insights or knowledge using systematic and transparent methods. Another example of a narrative synthesis approach is described by Greenhalgh et al [14]. These were referred to as traditions.

A chronology and narrative or story was built up for each of these, and the findings from each tradition related to one another by identifying common themes, factors and explanations. This provided the basis for a conceptual model mapping all the evidence and showing empirical gaps as well as salient theories.

Quantitative data are transformed into qualitative form, for example by extracting concepts or key findings. These approaches use qualitative methods of analysis, such as thematic analysis. Synthesis can be conducted using meta-ethnography or the qualitative cross-case methods. Cross-case analysis usually uses some form of chart or matrix [15] to display summarised material from several studies to facilitate comparison of the findings.

Using such displays it is possible to group together key concepts and identify core elements to develop new concepts or explanations [16]. Meta-ethnography involves induction and interpretation i. This is achieved by reciprocal translation — a process similar to constant comparison in primary qualitative research, which entails examining the concepts in each study looking for similarities and differences: This analysis continues until all the concepts have been translated into one another by matching, combining or adapting them and from this it may be possible to develop a line of argument a new theory or development of existing theory or a refutational synthesis which can explain opposing interpretations in the literature.

This theorised that patients deliberately modify and adapt their medication taking based on complex understandings and beliefs. Thus non-adherence with drug regimens does not simply reflect a passive failure to take medicines, but is the result of active decision making by the patient see Figure 1. Insert figure 1 about here Quantitative approaches Quantitative approaches to the synthesis of qualitative and quantitative findings from multiple studies integrate the research findings using statistical analysis methods.

This means that all the data need to be in numerical form, and thus any qualitative findings have to be converted into quantitative data. One way of doing this uses content analysis — a technique for categorising the data into themes which can then be counted and converted into frequencies to identify dominant issues across a number of studies.

The scores were examined against a range of characteristics of each site in a quantitative analysis and the sites were assigned to one of five hierarchical groups to help explain the relative success of the different pilots. The same approach could be used to synthesise findings from different studies as opposed to different study sites in a single study. Insert figure 2 about here Bayesian approaches These approaches apply the principles of Bayesian analysis to synthesis and are particularly relevant to undertaking syntheses designed for decision support.

One benefit of these approaches is that they can incorporate non-research sources of information such as expert or public opinion in addition to research evidence.

Synthesizing Quantitative Evidence for Evidence-based Nursing: Systematic Review.

In such approaches the data from multiple studies are converted into quantitative form and pooled for analysis and modelling. An example of a synthesis which used this approach is a study using qualitative and quantitative evidence to assess factors affecting uptake of immunisation [22]. These derived prior probabilities were combined with probabilistic data from quantitative studies and analysed to identify and rank a wide range of factors linked to uptake of immunisation. Other forms of Bayesian influenced approaches to synthesis include Bayesian approaches to cost-effectiveness analysis CEA which allow the use of non-trial evidence to inform decisions about the likely cost-effectiveness of particular treatments when they are applied in a specific context [23].

By adopting such an approach, a wider range of evidence non-research as well as research based can be incorporated into the synthesis along with the explicit value judgements necessary to identify the best course of action for decision makers [13] Discussion Many of the methods for research synthesis are evolving [24].

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Several were developed as methods for integrating primary data, usually from a single methodological approach, be it qualitative or quantitative. Some, like meta-ethnography, have only relatively recently been applied to health care. As we have shown there is a range of terminology in use, some of which can be confusing — terms such as narrative review, literature review, systematic review and narrative synthesis are sometimes used interchangeably, but can refer to quite distinct approaches. For knowledge support, there are a range of synthesis approaches that might be employed, and the choice of method may depend on the nature of the question and the form of the evidence qualitative or quantitative or both, and whether non-research sources are to be included.

For decision support syntheses, there are fewer available methods and the synthesis will have to be clearly tailored to the demands of the decision-making process. It seems likely that the kinds of research synthesis required in a health care policy and management context will, for the moment at least, need to use a combination of approaches so that a range of different types of evidence can be considered simultaneously. Given that qualitative and quantitative research often addresses quite different questions it may be that in many cases a synthesis across the qualitative-quantitative boundary is unnecessary.

Whatever the route, the aim, for researchers, policy-makers and managers is implicit in the definition of synthesis, that is to move us from policy problems and goals towards a conclusion in terms of policy options. Systematically reviewing qualitative and quantitative evidence to inform management and policy-making in the health field. Using realist methods to produce syntheses of evidence for use by managers and policy makers.

Towards systematic reviews that inform health care management and policy-making. Synthesising qualitative and quantitative evidence: The Cochrane is a group of over 37, specialists in healthcare who systematically review randomised trials of the effects of prevention, treatments and rehabilitation as well as health systems interventions. When appropriate, they also include the results of other types of research. The Cochrane Collaboration provides a handbook for systematic reviewers of interventions which "provides guidance to authors for the preparation of Cochrane Intervention reviews.

The Cochrane Collaboration logo visually represents how results from some systematic reviews can be explained. The quasi-standard for systematic review in the social sciences is based on the procedures proposed by the Campbell Collaboration , which is one of a number of groups promoting evidence-based policy in the social sciences.

The Campbell Collaboration "helps people make well-informed decisions by preparing, maintaining and disseminating systematic reviews in education, crime and justice, social welfare and international development.

The Campbell Collaboration was created in and the inaugural meeting in Philadelphia, USA, attracted 85 participants from 13 countries. Due to the different nature of research fields outside of the natural sciences, the aforementioned methodological steps cannot easily be applied in business research. Early attempts to transfer the procedures from medicine to business research have been made by Tranfield et al.

Synthesizing Quantitative Evidence

Based on the experiences they have made in their own discipline, these authors have adapted the methodological steps and developed a standard procedure for conducting systematic literature reviews in business and economics. While systematic reviews are regarded as the strongest form of medical evidence, a review of studies found that not all systematic reviews were equally reliable, and that their reporting can be improved by a universally agreed upon set of standards and guidelines. Roberts and colleagues highlighted the problems with systematic reviews, particularly those conducted by the Cochrane , noting that published reviews are often biased, out of date and excessively long.

They proposed several solutions, including limiting studies in meta-analyses and reviews to registered clinical trials, requiring that original data be made available for statistical checking, paying greater attention to sample size estimates, and eliminating dependence on only published data. Some of these difficulties were noted early on as described by Altman: Systematic reviews are increasingly prevalent in other fields, such as international development research.

From Wikipedia, the free encyclopedia. For the academic journal, see Systematic Reviews. This article is missing information about History.

Please expand the article to include this information. Further details may exist on the talk page. Retrieved 18 November Centre for Evidence Based Medicine. Archived from the original on CRD's guidance for undertaking reviews in health care.

University of York , Centre for Reviews and Dissemination, Systematic reviews in the social sciences. Ader ; Gideon J. Mellenbergh ; David J. Advising on Research Methods: Johannes van Kessel Publishing. Standards for Systematic Reviews".

Noteworthy

Retrieved 2 June Retrieved 1 June What Are Systematic Reviews? Cochrane Consumers and Communication. Journal of Clinical Epidemiology. Check date values in: Sao Paulo Medical Journal. Why and for whom?

Retrieved 6 October Cochrane Consumers and Communication". Archived from the original on February 3, Retrieved March 26, British Journal of Management.

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