Increasing response rates to postal questionnaires: systematic review.
OBJECTIVE
To identify methods to increase response to postal questionnaires.


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


METHODS
292 randomised controlled trials including 258 315 participants INTERVENTION REVIEWED: 75 strategies for influencing response to postal questionnaires.


METHODS
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.
Edwards
Phil
P
CRASH Trial Co-ordinating Centre, Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London WC1B 1DP. phil.edwards@lshtm.ac.uk
Roberts
Ian
I
Clarke
Mike
M
DiGuiseppi
Carolyn
C
Pratap
Sarah
S
Wentz
Reinhard
R
Kwan
Irene
I
D003625:Data Collection / Q000191:economics / Q000379:methods; D003627:Data Interpretation, Statistical; D006801:Humans; D009042:Motivation; D011177:Postal Service; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D011795:Surveys and Questionnaires