Resumen de Improving Survey Participation: Cost Effectiveness of Callbacks to Refusals and Increased Call Attempts in a National Telephone Survey in France

Stéphane Legleye, Géraldine Charrance, Nicolas Razafindratsima, Aline Bohet, Nathalie Bajos, Caroline Moreau

• The general decrease in telephone survey response rates leads to potential selection and estimation biases. As nonrespondents can be broken down into noncontacts and refusals, different strategies can be deployed�increasing the number of call attempts before abandoning a number, and calling back refusals/abandonments to persuade them to participate. Using a two-stage random-digit-dialing sample of 8,645 individuals aged 15�49 for a survey on sexual and reproductive health (SRH), we compared the effects of the two strategies: including hard-to-contact respondents (more than twenty call attempts with no upper limit) and including respondents from two successive waves of call-back among initial refusals/abandonments. Comparisons were based on sociodemographic bias, differences in SRH behaviors, multivariate logistic modeling of SRH behaviors, post-calibration weighting, and cost estimation. The sociodemographic profile of hard-to-contact and call-back respondents differed from that of easy-to-interview respondents. Including hard-to-contact respondents decreased the socio- demographic bias of the sample, while including call-back respondents increased it. Several significant differences in SRH behaviors emerged between easy-to-interview and hard-to-contact respondents, but none between first-wave and call-back respondents. Nevertheless, the determinants of SRH behaviors in call-back and hard-to-contact respondents differed with respect to easy-to-interview respondents. The trade-off between bias and financial costs suggests that the best protocol would be to mix the two strategies but with only one call-back wave involving a limited number of call attempts to achieve a sufficient sample size with optimal quality.