Skip to Main Content
MCPHS Library Logo

*Evidence-Based Medicine Resources

This guide focused on the "acquire" stage of evidence-based medicine and the resources and search strategies to support this process.

Models for Levels of Evidence

Evidence is arranged into levels or a hierarchy (sometimes displayed as a pyramid), and studies are assigned to different levels based on the methodological quality of their design, and validity. There are several evidence rating scales available to use, including:

Levels of Evidence by Study Type

Evidence Level Study Type
One Systematic review or meta-analysis of all relevant randomized trials (RCTs)
Two Well-designed RCTs
Three Well-designed controlled trials without randomization
Four Well-designed case-control and cohort studies
Five Systematic review of descriptive and qualitative studies
Six A single descriptive or qualitative study
Seven The opinion of authorities and/or reports of expert committees


Connect with the MCPHS Libraries via Social Media: Instagram