Response patterns in the Belgian health interview survey: web versus face-to-face mode

Abstract

Abstract Background Potential is seen in web data collection for population health surveys due to a combination of its cost-effectiveness and ease of implementation and the increased internet penetration rates. Nonetheless, web modes may lead to lower and more selective unit response rates than traditional modes such as face-to-face (F2F) interviewing and hence may increase bias in the measured indicators. This research assesses the response patterns of a web versus F2F study. Methods A Belgian health interview survey by web (BHISWEB; net sample=1010) was organized parallel to the traditional F2F BHIS 2018 (BHIS2018; net sample=11611; subsample used in this study=2748). Socio-demographic data on invited individuals were obtained from the national register and census linkages. To address the high item-missingness on education level deriving from the census, multiple imputation (m = 20) was applied. Unit response rates considering the different sampling probabilities of both surveys were calculated. Logistic regression analyses examined the impact of mode (web vs. F2F) and interactions between mode and socio-demographic characteristics on unit response. Results The unit response rate was significantly lower in the BHISWEB (18.0% (95% CI: 17.0-19.1)) than in the BHIS2018 (43.1% (95% CI: 41.5-44.7)). A lower web versus F2F response rate was found among all socio-demographic groups, however, this lower web response was less pronounced among youngsters, people cohabiting with household members, higher educated people and native Belgians. Conclusions The F2F unit response rate was generally higher, yet for certain groups the difference between web versus F2F was smaller. It is therefore worthwhile to experiment with adaptive mixed-mode designs to optimize resources without increasing selection bias; e.g. only inviting socio-demographic groups more eager to participate online for web surveys (e.g. youngsters) while remaining to focus on increasing the F2F response rates for other groups. Key messages The advantages of web versus F2F interviewing come against its considerable lower unit response rate. Differences in unit non-response between web and F2F vary between socio-demographic groups.