Table 4 Risk of bias assessment
Author | Study participation | Study attrition | Prognostic factor measurement | Outcome measurement | Study confounding | Statistical Analysis and reporting | Overall risk of bias |
|---|---|---|---|---|---|---|---|
Delgado (2015) | Low | Moderate | Low | Moderate | Moderate | Low | Moderate |
Farmer (2013) | Moderate | Moderate | Moderate | Moderate | Moderate | Low | Moderate |
Harper (1998) | Moderate | High | High | Moderate | High | Moderate | High |
O’Brien (1987) | Moderate | High | Moderate | Moderate | Moderate | Low | Moderate |
White-Williams (2013) | Moderate | Moderate | Moderate | Low | Low | Low | Low |