Variations in general practitioners' response to postal questionnaires.

Postal questionnaires offer an efficient method of collecting information. They are cheap and relatively quick and can be widely scattered geographically. In approaching professional groups there are no problems of illiteracy or inarticulateness to set against these advantages. The main difficulty then is often the response rate. With general practitioners the problem of response is often thought to be particularly acute because of the vast amount of commercial literature coming through their letter boxes. Even so high proportions have responded to certain studies. Some variations are shown in Table I. The studies quoted vary from a single Yes/No question on a plebiscite sponsored by the B.M.A. about opening negotiations on the health service to a 24-page questionnaire from two American research workers who were visitors to Britain. The response was 88 per cent. to the first and 60 per cent. to the second, but this last was increased to 73 per cent. when a shorter questionnaire, with 34 questions, was sent to those who had not replied. The subject of the inquiry and the sponsoring organization are generally supposed to influence response rates. Another hypothesis is that there is an increasing resistance to surveys so that response rates are now lower than they were a few years ago. But if an organization wants information about a particular subject these things are fixed. Other possible ways of influencing the response are: Length of questionnaire Number or spacing of reminders Colour and size of envelopes Type-written/hand-written envelopes Number and denomination of stamps Tone of accompanying letter-authoritarian/ persuasive Layout of questionnaire and method of recording answers Introduction of appealing "throw-away" questions Space for recording qualifications and comments Day of week and/or season of year in which questionnaires are sent out In addition there is the content of the accompanying letter, which may emphasize the value of the study, the importance of a high response, the confidentiality , and the credentials of the sponsors. Offers can be made to send the results, to come and discuss the study personally, or to send more information about the study or sponsoring organization. Many investigators have their own recipe for success, but