If the outcome of a randomised controlled trial suggests something, we are more likely to take notice than if it were published in a case report. The weight of evidence of a randomised controlled trial is larger than that of a case report. Consequently, there is hierarchy of evidence.
The hierarchy of evidence is as follows:
- Case report
- Cross sectional study
- Case control study
- Cohort study
- Randomised controlled trial
- Systematic review & meta-analysis