Evidence Synthesis Guide : Review Types & Decision Tree

See Right Review and Covidence's Understanding Review Types in Research eBook for descriptions of additional quantitative and qualitative review types.

​​Systematic Review

• A methodical and comprehensive literature synthesis focused on a well-formulated research question.
• Compares, evaluates, and synthesizes published and unpublished evidence in a search for the effect of an intervention.
• Designed for high sensitivity; commonly producing a large number of search results.
• 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.
   

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.
   

​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. 
• May take longer than a systematic review.
   

​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.
   

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.

Narrative/Literature Review

• A broad term referring to reviews with a wide scope and non-standardized methodology. 
• Aim is specificity; search results are not comprehensive and are narrowly focused on the topic.
• Search strategies, comprehensiveness, and time range covered will vary and do not follow an established protocol.

The descriptions and decision tree presented further below are based on content developed by Cornell University Library.