How Serious Is Nonresponse Bias in Advertising Conversion Research?

Abstract
The results from three advertising conversion studies are presented. Mail questionnaires were sent to advertising coupon inquirers in each study. Nonrespon dents of first and second questionnaire mailings were less likely to visit compared to the respondents of the first questionnaire mailings. Respondents from second and third compared to first mailings who did convert into visitors had different travel behavior patterns.