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Evidence-based practice involves multiple levels of evidence. Different levels of evidence may carry different levels of weight in order to make informed health-related decisions. Placing studies on this pyramid helps us put the results of a study's design into perspective, based on the strengths and weaknesses of the a study's design.

​Study designs are placed into a hierarchy based on their reliability known as the Levels of Evidence. As you go up the pyramid, each level represents increasing rigor, quality, and reliability of evidence produced by the different types of study design. This article explains each level of the pyramid in detail. Filtered information has gone through an evaluation process, with clinical experts appraising the evidence. 

Evidence-based Medicine Pyramid (University of Canberra Library, n.d.)

  • Level 1 - Information & opinion
  • Level 2 - Case studies or case reports
  • Level 3 - Cohort or longitudinal studies
  • Level 4 - Randomized Controlled Trials (RCT)
  • Level 5 - Critically appraised reviews and Reports
  • Level 6 - Systematic review - Compare all the evidence available
  • Level 7 - Meta-analysis

Image retrieved from University of Canberra Library (n.d.).

High levels of evidence may not be available or exist yet on certain topics. Less information will be available for more specialized questions with less clinical evidence. 

The top level of the pyramid begins with evidence from Meta-Analysis, including systematic review of results, and methods that are quantitative. A systematic review is when the authors have systematically evaluated and reviewed all available literature and research evidence on a given topic. When multiple authors collaborate to critically appraise, evaluate, and synthesize a number of research studies, they critically appraise a topic. Critically appraising articles involves multiple authors appraising and summarizing individual studies. Randomized Controlled Trials (RCT) groups patients into randomized groups, an experimental group and a control group. The outcomes of interest are followed amongst the groups. Cohort Studies examine two groups or cohorts of patients, those who receive the exposure of interest and those who do not. The outcomes are evaluated over time. Case-control studies identify patients with the outcome of interest and those without the outcome, and then studies the two groups and looks for exposures of interest. Background information or expert opinion evidence is the weakest level of the pyramid. This evidence includes handbooks, encyclopedias, and textbooks. Although these sources are valuable for summarized and foundational knowledge, this information is often generalized information about a topic or condition, as well, it can takes years for this information to be published which can interfere with the currency of evidence-based information. Experts do offer valuable opinions and thoughts on topics, but onions do not hold enough evidence to be considered filtered information. 

Winona State University Library. (2019, September 12). Evidence Based Practice Toolkit. Retrieved from


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