Types of Evidence Synthesis
Types of Evidence Synthesis
Evidence synthesis refers to any method of identifying, selecting, and combining results from multiple studies. For help selecting a methodology, try Cornell University's review methodology decision tree.
Types of evidence synthesis include:
Systematic Review
- Systematically and transparently collect and categorize existing evidence on a specific question of scientific, policy, or management importance.
- Compares, evaluates, and synthesizes evidence in a search for the effect of an intervention.
- Time-intensive and often take months to a year or more to complete.
- The most commonly referred to type of evidence synthesis. Sometimes confused as a blanket term for other types of reviews.
Literature (Narrative) Review
- A broad term referring to reviews with a wide scope and non-standardized methodology.
- Search strategies, comprehensiveness, and time range covered will vary and do not follow an established protocol.
Scoping Review or Evidence Map
- Systematically and transparently collect and categorize existing evidence on a broad question of scientific, policy or management importance.
- Seeks to identify research gaps and opportunities for evidence synthesis rather than searching for the effect of an intervention.
- May critically evaluate existing evidence, but does not attempt to synthesize the results in the way a systematic review would. (see EE Journal and CIFOR)
- May take longer than a systematic review.
- See Arksey and O'Malley (2005) for methodological guidance.
Rapid Review
- Applies Systematic Review methodology within a time-constrained setting.
- Employs methodological "shortcuts" (limiting search terms for example) at the risk of introducing bias.
- Useful for addressing issues needing quick decisions, such as developing policy recommendations.
- See Evidence Summaries: The Evolution of a Rapid Review Approach
Umbrella Review
- Reviews other systematic reviews on a topic.
- Often defines a broader question than is typical of a traditional systematic review.
- Most useful when there are competing interventions to consider.
Meta-analysis
- Statistical technique for combining the findings from disparate quantitative studies.
- Uses statistical methods to objectively evaluate, synthesize, and summarize results.
- May be conducted independently or as part of a systematic review.