Increasing response rates to postal questionnaires: systematic reviewBMJ 2002; 324 doi: https://doi.org/10.1136/bmj.324.7347.1183 (Published 18 May 2002) Cite this as: BMJ 2002;324:1183
- Phil Edwards, senior research fellow ()a,
- Ian Roberts, professor of epidemiology and public healtha,
- Mike Clarke, associate director (research)c,
- Carolyn DiGuiseppi, associate professor of preventive medicine and biometricsd,
- Sarah Pratap, research fellowb,
- Reinhard Wentz, information specialistb,
- Irene Kwan, research fellowb
- a CRASH Trial Co-ordinating Centre, Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London WC1B 1DP
- b Cochrane Injuries Group, Department of Epidemiology and Population Health
- c UK Cochrane Centre, Oxford OX2 7LG
- d Department of Preventive Medicine and Biometrics, University of Colorado Health Sciences Center, Campus Box C245, 4200 East Ninth Avenue, Denver, CO 80262, USA
- Correspondence to: P Edwards
- Accepted 2 December 2001
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.
What is already known on this topic
What is already known on this topic Postal questionnaires are widely used in the collection of data in epidemiological studies and health research
Non-response to postal questionnaires reduces the effective sample size and can introduce bias
What this study adds
What this study adds This systematic review includes more randomised controlled trials than any previously published review or meta-analysis no questionnaire response
The review has identified effective ways to increase response to postal questionnaires
The review will be updated regularly in the Cochrane Library
Funding The study was supported by a grant from the BUPA Foundation and a Nuffield Trust short term fellowship.
Competing interests None declared
- Accepted 2 December 2001