Librarian
Levels of Evidence / Evidence Hierarchy
Levels of evidence (sometimes called hierarchy of evidence) are assigned to studies based on the research design, quality of the study, and applicability to patient care. Higher levels of evidence have less risk of bias.
Levels of Evidence (Melnyk & Fineout-Overholt 2023)
|
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 |
*Adapted from: Melnyk, & Fineout-Overholt, E. (2023). Evidence-based practice in nursing & healthcare: A guide to best practice (Fifth edition.). Wolters Kluwer.
Levels of Evidence / Evidence Hierarchy
Levels of Evidence (LoBiondo-Wood & Haber 2022)
Level |
Research Designs |
|---|---|
| 1 | Systematic Review or meta-analysis of RCTs (randomized control trials) |
| 2 | Randomized control trials |
| 3 | Quasi-experimental Studies |
| 4 | Non-experimental studies |
| 5 | Meta-synthesis |
| 6 | Qualitative studies |
| 7 | Expert opinions: reports from expert panels and organizations, not based on research |
Adapted from LoBiondo-Wood, G. & Haber, J. (2022). Nursing research: Methods and critical appraisal for evidence-based practice (10th ed.). Elsevier.
Evidence Pyramid (Levels of Evidence)
"Evidence Pyramid" is a product of Tufts University and is licensed under BY-NC-SA license 4.0
Tufts' "Evidence Pyramid" is based in part on the Oxford Centre for Evidence-Based Medicine: Levels of Evidence (2009)
Definitions
- SAGE Research Methods: Foundations This link opens in a new windowProvides introductory overviews to major research methodologies, research ethics, and biographical sketches of researchers.
Encyclopedia of Nursing Research by Call Number: eBookISBN: 9780826133045Publication Date: 2017-07-01Comprehensive and concise, entries provide the most relevant and current research perspectives and demonstrate the depth and breadth of nursing research today. This one-stop reference presents key terms and concepts and clarifies their application to practice. The fourth edition has been substantially updated to contain the latest research for nurse scientists, educators, and students in all clinical specialties.
