NASA categories of evidence

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NASA Categories of Evidence comprise a matrix or scale denoting the sources of evidence provided in the Human Research Program's various evidence reports, and thus potentially their probative value and efficacy. [1] Authors in the Program were urged to label their evidence according to whether it was based on controlled experiments, observation, or expert opinion.

Broad "Experimental" Design TypeSilagy & Haines Levels of Evidence [2] Nasa Categories of Evidence
ControlledIa - Meta-analysis of randomized trials I - At least one randomized, controlled trial
Ib - At least one randomized trial
IIa - At least one controlled study without randomization II - At least one controlled study without randomization, including cohort, case-control, or subject operating as own control.
IIb - At least one other quasi-experimental study
ObservationalIII - Non-experimental descriptive studies, e.g. comparative correlation or case studies.III - Non-experimental observations or comparative, correlation, and case or case-series studies.
Opinion IV - Expert committee reports or opinions or clinical experiences of respected authorities.IV - Expert committee reports or opinions of respected authorities based on clinical experiences, bench research, or "first principles".

References

  1. NASA Categories of Evidence
  2. Silagy, C; Haines, A (2001). Evidence Based Practice in Primary Care (PDF) (2nd ed.). London: BMJ Books.