JUNE 20, 2002

Increasing response rates to postal questionnaires, a meta-analysis

Phil Edwards, Ian Roberts, Mike Clarke, Carolyn DiGuiseppi, Sarah Pratap, Reinhard Wentz and Irene Kwan have prepared an excellent article entitled "Increasing response rates to postal questionnaires: systematic review" which is available on-line at bmj.com. Here is the short version of the work accomplished and of the conclusions reached.

Objective: To identify methods to increase response to postal questionnaires.

Design: Systematic review of randomised controlled trials of any method to influence response to postal questionnaires.

Studies reviewed: 292 randomised controlled trials including 258,315 participants.

Intervention reviewed: 75 strategies for influencing response to postal questionnaires.

Main outcome measure: The proportion of completed or partially completed questionnaires returned.

Results: The odds of response were more than doubled when a monetary incentive was used (odds ratio 2.02; 95% confidence interval 1.79 to 2.27) and almost doubled when incentives were not conditional on response (1.71; 1.29 to 2.26). Response was more likely when short questionnaires were used (1.86; 1.55 to 2.24). Personalised questionnaires and letters increased response (1.16; 1.06 to 1.28), as did the use of coloured ink (1.39; 1.16 to 1.67). The odds of response were more than doubled when the questionnaires were sent by recorded delivery (2.21; 1.51 to 3.25) and increased when stamped return envelopes were used (1.26; 1.13 to 1.41) and questionnaires were sent by first class post (1.12; 1.02 to 1.23). Contacting participants before sending questionnaires increased response (1.54; 1.24 to 1.92), as did follow up contact (1.44; 1.22 to 1.70) and providing non-respondents with a second copy of the questionnaire (1.41; 1.02 to 1.94). Questionnaires designed to be of more interest to participants were more likely to be returned (2.44; 1.99 to 3.01), but questionnaires containing questions of a sensitive nature were less likely to be returned (0.92; 0.87 to 0.98). Questionnaires originating from universities were more likely to be returned than were questionnaires from other sources, such as commercial organisations (1.31; 1.11 to 1.54).

Conclusions: Health researchers using postal questionnaires can improve the quality of their research by using the strategies shown to be effective in this systematic review.

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