Wilson 1996c.
| Methods | Same as Wilson 1996a | |
| Participants | — | |
| Interventions | — | |
| Outcomes | — | |
| Notes | — | |
| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Adequate sequence generation | Low risk | Same as Wilson 1996a |
| Allocation concealment | Unclear risk | — |
| Blinding of study subjects | Low risk | — |
| Blinding of outcome assessor | Unclear risk | — |
| Incomplete outcome data (attrition bias) | Unclear risk | — |
| Selective outcome reporting (reporting bias) | Low risk | — |
| Outcome measure (combined air and water test used?) | High risk | — |
OP = operation