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Table 3 Subgroup analysis

From: Does a monetary incentive improve the response to a postal questionnaire in a randomised controlled trial? The MINT incentive study

  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)