Level of evidence | Type of evidence |
---|---|
1a | Evidence obtained from meta-analysis of randomized trials |
1b | Evidence obtained from at least one randomized trial |
2a | Evidence obtained from one well-designed controlled study without randomization |
2b | Evidence obtained from at least one other type of well-designed quasi-experimental study |
3 | Evidence obtained from well-designed non-experimental studies, such as comparative studies, correlation studies, and case reports |
4 | Evidence obtained from expert committee reports or opinions or clinical experience of respected authorities |