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A randomized trial of incentives to improve response rates to a mailed women's health questionnaire
Maura K Whiteman1, Patricia Langenberg, Kristen Kjerulff
1Department of Epidemiology and Preventive Medicine, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA.
Background:
Mailed questionnaires can be a convenient method for collecting data on women's health, although poor response rates are a concern.
Methods:
As part of a survey of women's health conducted in Maryland in 2001, a randomized trial was performed to assess the effects of two incentives (US dollars 1.00 or a lottery ticket) as well as precontact with an introductory postcard on response rates. Questionnaires were mailed to 3000 women aged 40-60 who were randomized to one of six incentive/precontact groups: lottery/postcard, money/postcard, postcard only, lottery only, money only, or no incentive/no postcard.
Results:
The overall response rate was 37.6%. Each incentive/precontact group yielded a higher response rate than the no incentive/no postcard group, although only the response rates for the lottery/postcard group (41.3%) and the money only group (40.0%) were significantly higher than that of the no incentive/no postcard group (33.1%). Money was the only factor that had a significant independent effect on likelihood of response (hazards ratio [HR] compared to no incentive = 1.22, 95% confidence interval [CI] = 1.03, 1.43). Response rates were lower in minority ZIP codes, although the effects of the incentives were generally greater than in the nonminority ZIP codes.
Conclusions:
These results indicate that response rates to mailed women's health questionnaires may be improved with modest incentives, particularly cash incentives.
