Effects of Filter Questions in Public Opinion Surveys GEORGE F. BISHOP, ROBERT W. OLDENDICK
A N D ALFRED J. TUCHFARBER
Do you have an opinion on this or not? Have you been interested enough in this to favor one side over the other? Where do you stand on this issue, or haven't you thought much about it? These questions typify the filters that have long been used in the American National Election Studies to screen out the politically uninformed, a practice which stems from the early concerns of Philip Converse (1964, 1970) and his colleagues with the problem of "non-attitudes" in political opinion surveys. Only recently, however, has anyone attempted to examine, systematically, the consequences of using such filter questions: Schuman and Presser (1978, 1981). Comparing filtered with unfiltered questions Abstract Extending previous work, the authors find that the wording of a filter question can make a significant difference in the percentage of "don't know" (DK) responses elicited by an item, especially with topics that are more abstract or less familiar to survey respondents. They also find, however, that the content of an item can have a substantial, independent effect on DK or "no opinion" responses, regardless of how the filter question is worded. In general, it appears that the less familiar the issue or topic, the greater the increase in DK responses produced by adding a filter. Even more important, the analysis shows that filtering can in some instances dramatically affect the conclusions a pollster would draw about the distribution of public opinion on an issue. Indeed, such effects may occur more often than has previously been suspected, though the circumstances under which they emerge remain elusive. The authors suggest that such effects may become amenable to analysis by probing respondents about "what they had in mind" as they answered the question. George F. Bishop is Associate Professor of Political Science and a Senior Research Associate at the Institute for Policy Research at the University of Cincinnati. Robert W. Oldendick is Assistant Director and Alfred J. Tuchfarber is Director of the Institute for Policy Research, University of Cincinnati. This research was supported by a grant from the National Science Foundation (SOC 78-07407). The authors want to thank the anonymous reviewers for their useful comments and suggestions for revising the original manuscript. Public Opinion Quarterly Vol. 47:528-546 0 1983 by the Trustees of Columbia Univers~ty Published by Elsevier Science Publ~shmgCo., Inc. 0033-362Xl8310047-528/$2.50