Nonresponse bias to mail survey questionnaires within a professional population.

Mail survey questionnaires are often used in dental research. In most instances, results depend on a single mailing and an incomplete return rate. The possible bias resulting from excluding nonresponders in tabuling data from mail survey questionnaires in a dentist population was investigated. Two different questionnaires, one soliciting attitudes, the other knowledge, were sent to randomly selected dentists. The differences between the responders and the nonresponders were analyzed with respect to the dentists' demographic data, attitudes, and knowledge. It was concluded that: (1) subject matter does affect dentist response rates to mailed survey questionnaires, (2) there are no differences in demographic data between dentist responders and nonresponders, and (3) nonresponse bias does not affect the results of dental surveys on a typical dentist response rate.