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Evidence-Based Medicine

Types of Studies

Meta-analysis: A systematic review that uses quantitative methods to synthesize and summarize results of studies.

Systematic Review: A summary of the medical literature that uses explicit methods to perform a comprehensive literature search and critical appraisal of individual studies and that uses appropriate statistical techniques to combine these valid studies.

Randomized Controlled Trial: A study in which participants are randomly allocated into an experimental group or control group and followed over time for the variables/outcomes of interest.

Cohort Studies: Involves identification of two groups (cohorts) of patients, one which recieved the exposure and one which did not, and following these cohorts forward for the outcome of interest.

Case Controlled Studies: A study which involves identifying patients who have the outcome of interest (cases) and patients without the same outcome (controls), and looking back to see if they had the exposure of interest.

Case Series: A report on a series of patients with an outcome of interest. No control group is involved.

Study Types for Clinical Questions

Type of Question           Suggested Study Type


Therapy/Prevention        RCT > cohort > case control > case series


Diagnosis                        prospective, blind comparison to a gold standard


Etiology/Harm                 RCT (or, if RCT is impractical or unethical) > cohort > case control > case series


Prognosis                        cohort > case control > case series

Subject Experts

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Kaitlyn Van Kampen
Clinical Librarian
Joseph Regenstein Library, Room 263
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Deb Werner
Director of Library Research in Medical Education
Joseph Regenstein Library, Room 268
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Holiday Vega
Librarian for Health, Psychology, and Social Work