Multiple-mode surveys can improve response and reduce survey error and costs. Although web surveys are an increasingly popular mode of survey administration, the full effect of web data collection on a primarily mail survey is not yet fully understood. This paper details response rates for a...

Web-surveys are more and more widespread due to their easiness and rapidity; nevertheless, the ones for which mailing lists are not used, cannot be scientifically valued as they show serious coverage errors. In fact, how it is underlined in par.2, the web-population P(w) represents only a subset...