Table 3 Subgroup analysis
| 4 month questionnaire | 8 month questionnaire | ||||
|---|---|---|---|---|---|
|
Incentive n = 590 (%) |
No incentive n = 604 (%) |
Incentive n = 480 (%) |
No incentive n = 470 (%) |
Interaction stats Ratio of RR, 4 months versus 8 months (95% CI) | |
| Questionnaire returned | 473 (80.2) | 435 (72.0) | 337(70.2) | 303 (64.5) |
1.02 (0.92, 1.14) |
| Questionnaire returned without chasing | 338 (57.3) | 287 (47.5) | 222 (46.3) | 206 (43.8) |
1.14 (0.96, 1.37) |
| Non-responder (after all follow-up efforts) | 46 (7.8) | 73 (12.1) | 50 (10.4) | 69 (14.7) |
0.91 (0.56, 1.48) |