Some experiments with factors that might affect the response of mothers to a postal questionnaire

The effects of a number of controllable factors on the response rate of mothers to a postal questionnaire were assessed by a series of experiments. In one a factorial design was used to look at seven factors with a random sample of 1600 mothers. The main findings were that the responses to questionnaires of 8, 16 or 24 pages were similar, but that rather more mothers replied when the questionnaires contained only factual questions than when they covered both facts and attitudes. Another experiment, based on a similar sample, compared the response rates when the questionnaires were sent out by a government organization or by the Institute for Social Studies in Medical Care, and found no difference. The final experiment looked at the effect of precoding the answers or asking respondents to tick boxes beside their replies and again found no difference in response rates. The overall response rate was 79 per cent, but this varied between 66 and 87 per cent in the ten randomly selected study areas--a much greater variation than that found with any of the experimental factors.