Strength of Evidence and Evidence Hierarchy:

Evidence/Strength Evidence Hierarchy
Level 1 Meta-analysis, Systematic reviews, Integrative reviews, Evidence-Based Practice Guidelines
(This level includes; research designs of Meta-Analyses, Systematic Reviews, Integrative Reviews, and EBP Guidelines which are developed from systematic reviews and housed in national repositories.)
Level 2 Randomized Controlled Trial (RCT) and Experimental designs (This level represents evidence from studies using a true experimental design.)

Strength of Evidence and Evidence Hierarchy:

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Level 3 Quasi-experimental designs (This level represents evidence obtained from experimental studies without randomization.)
Level 4 Non-experimental designs (This level represents evidence from well-designed non-experimental designs such as retrospective, case-control, cross-sectional, cohort-comparison, prospective, descriptive and correlational single studies.
Level 5 Meta-Synthesis (This level represents evidence from systematic reviews of studies using qualitative methods.)
Level 6 Single Qualitative Studies (This level represents single studies using a qualitative research approach.)
Level 7 Expert Opinion (This level represents materials from a variety of non-research based evidence and generally consists of reports of expert committees and/or opinions of authorities on the subject. The evidence from this level includes: specialists’ opinions, case studies, non-evidence-based practice guidelines, narrative reviews, editorials, regulations, legislation, and program outcome data/QI projects)