Nonresponse bias and cost-effectiveness in a Norwegian survey of family physicians.

Low response rates are a common problem in surveys of family physicians leading to uncertainty about the validity of results. In this study, the authors examined the association between multiple reminders and nonresponse bias, survey estimates and costs in a survey of family physicians in Norway (N = 3,463). After three postal reminders and one telephone follow-up, the response rate was 65.9%. They analyzed differences in nine demographic and practice variables between respondents and nonrespondents, the effect of nonresponse bias on survey estimates, and the cost-effectiveness of each reminder. Statistically significant differences between respondents and nonrespondents were found for six variables. However, demographic and practice variables had little association with the main outcome variables, and the overall survey estimates changed little with additional reminders. In addition, the cost-effectiveness of the final reminders was poor.