Table 3 Categories of evidence and its definitions
Categories | Definitions | Operational ranks |
|---|---|---|
Ia | Evidence from meta-analysis of randomized controlled trials | Rank A |
Ib | Evidence from at least one randomized controlled trial | |
IIa | Evidence from at least one controlled study without randomization | |
IIb | Evidence from at least one other type of Quasi-experimental study | |
III | Evidence from non-experimental descriptive studies, such as comparative studies, correlation studies, case-control studies and qualitative studies. | |
IV | Evidence from expert committee reports or opinions and / or clinical experience of respected authorities | Rank B-D |