Table 1 Grading system for strength of evidence
Strength of Evidence | Criteria |
|---|---|
Strong | ≥2 high-quality studies showing positive association between the presence of a variable and the outcome AND No studies showing a negative association |
Moderate | One high-quality AND one lesser-quality study showing association AND No studies showing negative association |
Weak | > 2 low-quality studies showing positive association OR Only one high-quality study showing positive association |
Negative | ≥ 1 high-quality study showing negative association (inverse relationship) AND No studies showing a positive association |
Inconclusive | Associations present in only one low-quality study OR No studies of any quality showing univariate association OR Presence of positive and negative associations from different articles, regardless of study quality |