| Methods |
RCT |
| Participants |
Various workers
n = 40
USA
Several companies |
| Interventions |
Intervention: fitting instructions for earplugs and earmuffs in step‐by‐step procedure; n = 20
Control: instructions on paper as provided by the manufacturer n = 20 |
| Outcomes |
Hearing thresholds with and without protection at 0.5, 1, 2, 3, 4, 6, 8 kHz |
| Notes |
Immediate |
| Risk of bias |
| Bias |
Authors' judgement |
Support for judgement |
| 14. Blinding (subjects) |
High risk |
no blinding |
| 15. Blinding (outcome assessors) |
High risk |
no blinding |
| 16. Retrospective unplanned subgroup analyses |
Low risk |
no additional analyses |
| 17. Follow‐up |
Low risk |
all 3 weeks |
| 18. Statistical tests |
Low risk |
ANOVA |
| 19. Compliance |
Low risk |
wearing of HPD checked |
| 20. Outcome measures |
Low risk |
audiometry quality reported |
| 21. Selection bias (population) |
Low risk |
same population |
| 22. Selection bias (time) |
Low risk |
same time |
| 23. Randomization |
Low risk |
subjects were randomly assigned |
| 24. Allocation concealment |
Unclear risk |
not reported, not applicable |
| 25. Adjustment for confounding |
Unclear risk |
not reported |
| 26. Incomplete outcome data |
Low risk |
no loss |
