Research Guide for

Evidence-Based Medicine


Evidence-Based Medicine

Hierarchy of Evidence

Understanding information, research, and reviewed research as a hierarchy helps in understanding EBM and EBP. Often you encounter background information and original research, which are the more common types of information available to you,

However, to find EBM information you have to look for meta-anlysis and systematic reviews. These types of information are at the top of the hierarchy of evidence pyramid, the pyramid is below and definitions of these different resources are at the right.

Quality of Evidence Pyramid


Data from multiple scholarly and peer reviewed research is statistically analyzed to identify relationships and compare and contrast results in order to test the research and better understand the findings.

Systematic Reviews

A review of multiple scholarly and peer reviewed research articles related to a topic. The reviewers identify the best quality research and evaluate, sythesize, and summarize the findings.

Randomized Control Trial

An experiment that tests the effectiveness of a treatment or medical intervention on subjects that are randomly assigned to either the control (no exposure to intervention) group or experimental (exposed to intervention) group.

Cohort Studies

A longitudinal study (data from study is collected over a period of time) of two groups (cohorts). One cohort is the control group; the other is exposed to the experiment. Data is collected over a period of time, usually many years. 

Cross-Sectional Study

A study where an intervention is observed and data is collected only at one point in time.

Case Reports

A narrative of a patient's symptoms, diagnosis, treatment, and outcomes.

Background Information and Expert Opinion

General and foundational knowledge on a topic or clinical question can be found in a variety of sources including electronic and print encyclopedias, dictionaries, and books.

Expert opinions are found in academic publications, journals, trade publications and books. They are expert opinion only if the author's credentials are provided and the author is respected and experienced in the field.