Table 4.
Costs
| 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 | |