|
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
|
