Public Opinion Quarterly Advance Access published online on December 9, 2008
Public Opinion Quarterly, doi:10.1093/poq/nfn061
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Does a Probability-Based Household Panel Benefit from Assignment to Postal Response as an Alternative to Internet-Only?
Address correspondence to Bryan Rookey; e-mail: bdrookey{at}wsu.edu
A potential limitation of web-only panels of the general public, even when households are selected using probability methods, is that only about 70 percent of U.S. households have members with Internet access. In addition, some members of Internet-connected households may be unable or unwilling to participate over the web. The Gallup Panel uses both web and mail modes to survey respondents and in 2006 included approximately 50,000 households selected by random-digit dialing. Frequent Internet users were assigned to respond by the web, while others were assigned to participate by mail using a paper questionnaire with a similar visual layout to the web. We use several approaches to determine whether or not the mail option adds value to the results in an otherwise Internet panel and organize our analyses around answering a series of questions. First, does the use of mail allow different types of people to be included? Second, do mail and web respondents give different answers to the same questions? Third, does weighting on and controlling for demographics eliminate any differences in responses from mail and web respondents and indicate that mail is not needed? Finally, do differences exist when responses are collected using an independent mode? In general, the answers to these questions suggest that use of mail adds value to the panel results and improves the overall accuracy of survey results.
BRYAN D. ROOKEY AND DON A. DILLMAN are with Social and Economic Sciences Research Center, Washington State University, P.O. Box 644014, Pullman, WA 99164-4014, USA. STEVE HANWAY is with The Gallup Organization, 901 F Street NW, Suite 400, Washington, DC, USA. We gratefully acknowledge with thanks help with earlier versions of the paper provided by Julie Curd, Darby Miller Steiger, Larry Curd, and Ron Bartholomew of The Gallup Organization; Zac Arens, formerly of The Gallup Organization; and Jolene Smyth at the University of Nebraska-Lincoln. Analysis of these data was supported by funds provided by The Gallup Organization to the Social and Economic Sciences Research Center at Washington State University.