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Evidence Based Practice (EBP): Critical Appraisal of Study Designs

Introduction to Study Design

Types of Evidence and Study Designs


Pyramid of Evidence

Pyramid of Evidence. Source: “EBM Pyramid.” Digital Image. Eli M. Oboler Library, 27 May 2016.

Source: “EBM Pyramid.” Digital Image. Eli M. Oboler Library, 27 May 2016.


Filtered Information (secondary literature)

Systematic review
Uses explicit, rigorous methods to identify, critically appraise, and synthesize relevant studies

Meta analysis
A quantitative method of combining the results of independent studies and synthesizing summaries and conclusions which may be used to evaluate therapeutic effectiveness.

Critically Appraised Topic
A summary of the current best evidence on a topic, generally by topic experts. Critically appraised topics (CAT's) usually include evidence from more than one study, but are more brief and their methods less rigorous than systematic reviews.

Critically Appraised Individual Article (a.k.a. Critically Appraised Paper)
A summary of a single paper, generally by a topic expert.


Unfiltered Information (primary literature)

Randomized controlled trial
A clinical trial that involves at least one test treatment and one control treatment, concurrent enrollment and follow up of the test- and control-treated groups, and in which the treatments to be administered are selected by a random process

Cohort study
Study in which subsets of a defined population are identified.

Case control trial
Study which start with the identification of persons with a disease of interest and a control group without the disease. The relationship of an attribute to the disease is examined by comparing diseased and non-diseased persons with regard to the frequency or levels of the attribute in each group.

Clinical trial
Pre-planned studies of the safety, efficacy or optimum dosage schedule of one or more diagnostic, therapeutic or prophylactic drugs, devices or techniques, selected according to predetermined criteria of eligibility and observed for predefined evidence of favorable and unfavorable effects.

Maps and Directions