VCU Libraries

Research Guides

Evidence-Based Practice

Appraise the Evidence

Not all research evidence is the same. There are lots of ways to study a health condition or intervention. The study design influences the quality of evidence. Pyramids are often used to show the quality of different types of studies. To find the best evidence, start with resources at the top of the pyramid. 

This first pyramid gives a broad overview of the relative quality of different types of evidence to support clinical decision-making: studies, synopses, syntheses, summaries and systems.

  • A single study examines a specific question in a limited population and results may not be relevant to other groups.
  • A synopsis summarizes evidence from a high-quality study or set of studies; synopses of multiple studies provide stronger evidence than synopses of a single study.
  • A synthesis, or systematic review is a comprehensive summary of all the evidence for a specific question.
  • Summaries are clinical guidelines or textbooks that are updated routinely to reflect complete and updated information about clinical issues.
  • Systems populated by many, many individual patient records represent the ideal source of evidence.

For more information, check out this webpage from McMaster University.

This pyramid shows the relative quality of different types of study designs. For example, randomized-controlled studies typically provide better evidence than observational studies, such as case control and cohort studies.