A systematic error introduced into survey research, for example, in intentions surveys, because some people in the sample do not respond to the survey (or to items in a questionnaire). Because those interested in the topic are more likely to respond, it is risky to assume that nonresponders would be similar to responders in reporting about their intentions. To avoid this bias, obtain high response rates. By following the advice in Dillman (2000), one should be able to achieve well over a 50% response rate for mail surveys, and often as much as 80%. To estimate nonresponse bias, try to get responses from a subsample of nonrespondents. Armstrong and Overton (1977) provide evidence showing than an extrapolation of trends across waves in responses to key questions, such as “How likely are you to purchase . . .?” will help to correct for nonresponse error.