Response rates to health-related surveys are declining. This study tested two strategies to improve the response rate to a health psychology survey mailed through English general practices: (1) sending a shortened questionnaire and (2) offering a monetary incentive to return a completed questionnaire.Design.
Randomized controlled trial.Methods.
Adults (n = 4,241) aged 45–59 years, from four General Practices in South-East England, were mailed a survey on attitudes towards bowel cancer screening. Using a 2 × 4 factorial design, participants were randomized to receive a ‘short’ (four A4 pages) or a ‘long’ (seven A4 pages) questionnaire, and one of four monetary incentives to return a completed questionnaire – (1) no monetary incentive, (2) £2.50 shop voucher, (3) £5.00 shop voucher, and (4) inclusion in a £250 shop voucher prize draw. Age, gender, and area-level deprivation were obtained from the General Practices.Results.
The overall response rate was 41% (n = 1,589). Response to the ‘short’ questionnaire (42%) was not significantly different from the ‘long’ questionnaire (40%). The £2.50 incentive (43%) significantly improved response rates in univariate analyses, and remained significant after controlling for age, gender, area-level deprivation, and questionnaire length. The £5.00 (42%) and £250 prize draw (41%) incentives had no significant impact on response rates compared to no incentive (38%).Conclusions.
A small monetary incentive (£2.50) may slightly increase response to a mailed health psychology survey. The length of the questionnaire (four pages vs. seven pages) did not influence response. Although frequently used, entry into a prize draw did not increase response. Achieving representative samples remains a challenge for health psychology.