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Research Methods Help Guide

Basic information on research methods concepts.


All definitions on this page are from the Study Design 101 tutorial created by the Himmelfarb Health Sciences Library. Go to the tutorial for much more information, examples, and self-assessments.

Use the resources located below each definition to find studies of that type in library databases and other resources. Hover over the database/resource name for information on applicable filters, limits, subjects, etc.

Note: although filters, limits, subjects, and other database options will help you focus your results to certain study types, rely on your own judgment when determining if a study matches the type you are seeking.

Case Report

An article that describes and interprets an individual case, often written in the form of a detailed story.

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Case Control Study

A study that compares patients who have a disease or outcome of interest (cases) with patients who do not have the disease or outcome (controls), and looks back retrospectively to compare how frequently the exposure to a risk factor is present in each group to determine the relationship between the risk factor and the disease.

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Cohort Study

A study design where one or more samples (called cohorts) are followed prospectively and subsequent status evaluations with respect to a disease or outcome are conducted to determine which initial participants exposure characteristics (risk factors) are associated with it. As the study is conducted, outcome from participants in each cohort is measured and relationships with specific characteristics determined.

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Randomized Controlled Trial

A study design that randomly assigns participants into an experimental group or a control group. As the study is conducted, the only expected difference between the control and experimental groups in a randomized controlled trial (RCT) is the outcome variable being studied.

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Practice Guideline

A statement produced by a panel of experts that outlines current best practice to inform health care professionals and patients in making clinical decisions. The statement is produced after an extensive review of the literature and is typically created by professional associations, government agencies, and/or public or private organizations.

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Systematic Review

A document often written by a panel that provides a comprehensive review of all relevant studies on a particular clinical or health-related topic/question. The systematic review is created after reviewing and combining all the information from both published and unpublished studies (focusing on clinical trials of similar treatments) and then summarizing the findings.

To find systematic reviews, refer to the following guide:


A subset of systematic reviews; a method for systematically combining pertinent qualitative and quantitative study data from several selected studies to develop a single conclusion that has greater statistical power. This conclusion is statistically stronger than the analysis of any single study, due to increased numbers of subjects, greater diversity among subjects, or accumulated effects and results.

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