Level | Rating | Criteria |
---|---|---|
Strong | +++ or −−− | Consistent findings in multiple studies of good methodological quality OR in one study of excellent methodological quality |
Moderate | ++ or −− | Consistent findings in multiple studies of fair methodological quality OR in one study of good methodological quality |
Limited | + or – | One study of fair methodological quality |
Conflicting | ± | Conflicting findings |
Unknown | ? | No studies or only studies of poor methodological quality |
+, positive result; –, negative result.