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Table 4 Costs

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

   Number
  Cost Incentive No incentive
Randomised   1070 1074
Initial mailing (printing, envelope, postage) £1.25 1070 1074
Incentive £5 1070 0
Repeat copy of mailing (printing, envelope, postage) £1.25 504 577
First follow-up phone call £0.90 808 844
Second follow-up phone call £0.90 497 578
Telephone data collection – unsuccessful £1.09 396 472
Telephone data collection – successful £6.54 101 115
Questionnaire returned £0.52 810 738
Cost per participant randomised   £9.35 £4.64
Cost per questionnaire returned   £12.35 £6.76