Davern, Michael E.

ObjectiveTo assess nonresponse bias in a mixed‐mode general population health survey.Data SourcesSecondary analysis of linked survey sample frame and administrative data, including demographic and health‐related information.Study DesignThe survey was administered by mail with telephone follow‐up to nonrespondents after two mailings. To determine whether an additional mail contact or mode switch reduced nonresponse bias, we compared all respondents (N = 3,437) to respondents from each mailing and telephone respondents to the sample frame (N = 6,716).Principal FindingsSwitching modes did not minimize the under‐representation of younger people, nonwhites, those with congestive heart failure, high users of office‐based services, and low‐utilizers of the emergency room but did reduce the over‐representation of older adults.ConclusionsMultiple contact and mixed‐mode surveys may increase response rates, but they do not necessarily reduce nonresponse bias.

Abstract Colorectal cancer (CRC) screening rates are often ascertained via self-reports but can be subject to overreporting bias. Asking about intention to get screened before asking about past screening may minimize overreporting of cancer screening. In a statewide survey conducted from July through October of 2005, we embedded an experiment that tested the effect of question ordering (asking about future intention to get screened before or after asking about past screening; “future first” and “future second,” respectively), crossed with survey mode (mail versus telephone), on CRC screening rates. Weighted analysis focused on 752 respondents who were ages 50 years or older. We found (a) that asking about future intentions to get screened before asking about past screening (future first) statistically significantly lowers reports of past CRC screening [70.9% future second versus 58.0% future first; odds ratio (OR), 1.83; 95% confidence interval (95% CI), 1.08-3.13]; (b) that there was no main effect of survey mode; and (c) that the effect of the ordering of the future intentions item varies by survey mode. In the mailed survey, the odds of reporting past CRC screening were almost thrice greater in the future second condition compared with the future first condition (72.4% versus 49.0%, respectively; OR, 2.74; 95% CI, 1.22-6.17). In the telephone condition, the odds of reporting were only 28% higher in the future second (69.5%) condition than in the future first condition (63.9%; OR, 1.28; 95% CI, 0.64-2.57). The results suggest that asking about future intentions to get screened before the actual behavior elicits lower, and arguably more truthful reports of CRC screening but mainly in mailed surveys. (Cancer Epidemiol Biomarkers Prev 2008;17(4):785–90)