An Experimental Comparison of Web and Telephone Surveys

Abstract

We carried out an experiment that compared telephone and Web versions of a questionnaire that assessed attitudes toward sci- ence and knowledge of basic scientific facts. Members of a random digit dial (RDD) sample were initially contacted by telephone and answered a few screening questions, including one that asked whether they had Internet access. Those with Intern et access were randomly assigned to complete either a Web version of the questionnaire or a computer- assisted telephone interview. Ther e were four main findings. First, although we offered cases assigned to the Web survey a larger incen- tive, fewer of them completed the online questionnaire; almost all those who were assigned to the telephone condition completed the interview. The two samples of Web users nonetheless had similar demographic characteristics. Second, the Web surv ey produced less item nonresponse than the telephone survey. The Web questionnaire prompted respon- dents when they left an item blank, whereas the telephone interviewers accepted no opinion answers without probing them. Third, Web respondents gave less differentiated an swers to batteries of attitude items than their telephone counterparts . The Web questionnaire presented these items in a grid that may have made their similarity more salient.