Nonresponse bias in a mail survey of physicians.

With the increased pressure on survey researchers to achieve high response rates, it is critical to explore issues related to nonresponse. In this study, the authors examined the effects of nonresponse bias in a mail survey of physicians (N = 3,400). Because slightly more than one half of the sample did not respond to the survey, there was potential for bias if nonresponders differed significantly from responders with respect to key demographic and practice variables. They analyzed response status and timing of response with respect to five variables: gender, region, specialty, urbanicity, and survey length. The potential consequences of nonresponse bias on the survey estimates were then analyzed. Men were more likely to respond, as were physicians receiving a shorter questionnaire. Repeated follow-up attempts reduced gender response bias because male physicians were more likely to be early responders. Overall, higher response rates were not associated with lower response bias.