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Critical Appraisal of Research Articles: Home

Online Resources

Which study design answers which questions best?

Etiology, Causation, Harm

Cohort study > Case control > Case Series > Cross sectional study

 Diagnostic Testing

Prospective, blind comparison to the gold standard


Cohort study > Case control > Case series

Therapy, Prevention

Randomized Controlled Trial (RCT) > Cohort > Case Control

What is Critical Appraisal?

"Critical appraisal is the process of systematically examining research evidence to assess its validity, results, and relevance before using it to inform a decision."

Hill, A. Spittlehouse, C. What is Critical Appraisal? What is...? series. Retrieved from

Types of Studies

Please see our tutorial, Study Design 101.

Randomized Controlled Trial (RCT)

A clinical trial involving one or more new treatments and at least one control treatment with specified outcome measures for evaluating the intervention.  The treatment may be a drug, device, or procedure. Controls are either placebo or an active treatment that is currently considered the "gold standard".  If patients are randomized via mathmatical techniques then the trial is designated as a randomized controlled trial.

Cohort Study

In cohort studies, groups of individuals, who are initially free of disease, are classified according to exposure or non-exposure to a risk factor and followed over time to determine the incidence of an outcome of interest.  In a prospective cohort study, the exposure information for the study subjects is collected at the start of the study and the new cases of disease are identified from that point on.  In a retrospective cohort study, the exposure status was measured in the past and disease identification has already begun. 

Case-control Study

Studies that start by identifying persons with and without a disease of interest (cases and controls, respectively) and then look back in time to find differences in exposure to risk factors. 

Cross-sectional Study

Studies in which the presence or absence of disease or other health-related variables are determined in each member of a population at one particular time. 


A quantitative method of combining the results of independent studies, which are drawn from the published literature, and synthesizing summaries and conclusions.

Systematic Review

A review which endeavors to consider all published and unpublished material on a specific question.  Studies that are judged methodologically sound are then combined quantitatively or qualitatively depending on their similarity.

Subject Guide

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Tom Harrod
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