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Levels of Evidence
Two Pyramids to Consider:
Image credit: University of Michigan Library used under Creative Commons Attribution License 4.0. Modified from: Haynes RB. Of studies, syntheses, synopses, summaries and systems: the “5S" evolution of services for evidence-based health care decisions. ACP J Club. 2006 Nov-Dec;145(3):A8-9.
Levels of Evidence: Numerical Approaches
Levels of Evidence
|
Level of Evidence |
Description |
| Level 1 |
Evidence from a systematic review or meta-analysis of all relevant RCTs (randomized controlled trials). |
|
Level 2 |
Evidence from at least one well-designed RCT (e.g. large multi-site RCT). |
|
Level 3 |
Evidence from a single well-designed controlled trials without randomization (aka quasi-experimental studies) OR a systematic review of a complete BOE (integrative review of higher and lower evidence) OR mixed methods intervention studies |
|
Level 4 |
Evidence from well-designed case-control or cohort studies |
|
Level 5 |
Evidence from systematic reviews of descriptive and qualitative studies (meta-synthesis) |
|
Level 6 |
Evidence from a single descriptive or qualitative study, EBP, EBQI and QI projects |
|
Level 7 |
Evidence from the opinion of authorities and/or reports of expert committees, reports from committees of experts and narrative and literature reviews |
Melnyk, & Fineout-Overholt, E. (2011). Evidence-based practice in nursing & healthcare: A guide to best practice (2nd edition.). Wolters Kluwer.