Criterion | Number of studies with | |||
---|---|---|---|---|
 | Low risk of bias | High risk of bias | Not possible to judge | Not applicable |
Comparison domain | 41 | 185 | – | – |
Control matching | 135 | 33 | 15 | 47 |
Effect modifiers | 169 | 46 | 12 | Â |
Measurement similarity | 205 | 10 | 11 | – |
Other confounding factors | 221 | 1 | 3 | – |