| UMich.edu | Levels of evidence ranging from 1 (systematic review and meta-analysis of randomized controlled trials) to 7 (expert opinion) |
| AHRQ.gov | Grading ranges from High (confident in effect of intervention) to Insufficient (unable to estimate or determine the effect) |
| CEBM.net | Evidence grading that ranges from 1a (systematic review of high quality studies) to 5 (expert opinion without critical appraisal) |
| Cochrane | GRADE approach ranges from from High to Very Low (the true effect is probably very different from the estimated effect) |
