CONTROLLED TRIAL OF THE EFFECT OF LENGTH, INCENTIVES, AND FOLLOW-UP TECHNIQUES ON RESPONSE TO A MAILED QUESTIONNAIRE

Mailed questionnaires are an economical method of data collection for epidemiologic studies, but response tends to be lower than for telepho ne or personal interviews. As part of a follow-up study of volunteers who provided a brief health history and blood sample for a blood speci men bank in 1989, the authors conducted a controlled trial of the effe ct of length, incentives, and follow-up techniques on response to a ma iled questionnaire. Interventions tested included variations on length of the questionnaire, effect of a monetary incentive, and effect of a postcard reminder versus a letter accompanied by a second questionnai re. Response was similar for the short (16-item, 4-page) and long (76- item, 16-page) questionnaire groups. The monetary incentive did not im prove the frequency of response. The second mailing of a questionnaire was significantly better than a postcard reminder in improving respon ses (23% vs. 10%). It is important to systematically test marketing pr inciples to determine which techniques are effective in increasing res ponse to mailed questionnaires for epidemiologic studies.