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Nursing Students' Guide to Evidence Based Research: Quality of Evidence Pyramid

Resources for Nursing Students

Quality of Evidence Pyramid

The infographic shows a pyramid constructed of 9 steps. Each level represents a stage in the development of knowledge about a medical topic. At each stage, the number of studies gets smaller, but the weight and value of the evidence increases. Here are the steps: Step 1: Background information, expert opinions, non-EBM guidelines [this is a pre-research stage]; Step 2: individual case reports; Step 3: case series or studies; Step 4: cohort studies [steps 2-4 are observational, or descriptive studies]. Step 5: non-randomized controlled trials; step 6: randomized controlled trials [steps 5 & 6 are experimental studies]. Step 7: critically appraised literature, evidence-based practice guidelines; Step 8: systematic reviews; Step 9: meta-analyses [steps 7-9 represent critical appraisal of the literature residing in the lower levels of the pyramid]. The arrow running up one side of the pyramid from the base to the apex shows how the value of the evidence increases, first as the number of subjects and the rigor of the studies increases, then as the medical community synthesizes and critically examines how these studies fit together to form a body of knowledge.