A mixture model for middle category inflation in ordered survey responses

Benjamin E. Bagozzi, Bumba Mukherjee

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17 Scopus citations


Recent research finds that, for social desirability reasons, uninformed individuals disproportionately give " neither agree nor disagree" type responses to survey attitude questions, even when a " do not know" option is available. Such " face-saving" responses inflate the indifference (i.e., middle) categories of ordered attitude variables with nonordered responses. When such inflation occurs within the middle category of one's ordered dependent variable, estimates from ordered probit (and ordered logit) models are likely to be unreliable and inefficient. This article develops a set of mixture models that estimate and account for the presence of " face-saving" responses in middle categories of ordered survey response variables, and applies these models to (1) simulated data and (2) a commonly studied survey question measuring attitudes toward European Union (EU) membership among individuals in EU-candidate countries. Results from the survey data set and the Monte Carlo experiments suggest that, when middle category inflation is present in one's ordered dependent variable, the estimates obtained from middle category mixture models are less biased than-and in some cases substantively distinct from-the estimates obtained from " naive" ordered probit models.

Original languageEnglish (US)
Pages (from-to)369-386
Number of pages18
JournalPolitical Analysis
Issue number3
StatePublished - Jul 2012

Bibliographical note

Funding Information:
Authors’ note: An earlier version of this article was presented as a poster at the 2011 Political Methodology Meeting. The authors wish to acknowledge the valuable suggestions that they received from the editor and reviewers of Political Analysis, Chris Zorn, Phil Schrodt, Will H. Moore, Daniel W. Hill, Eric Plutzer, John Freeman, Robert J. Franzese Jr., and the 2011 Political Methodology meeting attendees. This work was supported by the Pennsylvania State University’s College of Liberal Arts under the Forrest Crawford Graduate Scholarship. Replication materials can be found at Bagozzi and Mukherjee (2012). Supplementary Materials for this article are available on the Political Analysis Web site. 1Middle category responses include, e.g., “neither agree nor disagree” or “neither good nor bad.” 2Studies also show that respondents who are more uncertain about their position on certain policy issues are more likely to opt for the middle category response on survey questions that track their perception about their senator’s position on such issues (Bradey and Sniderman 1991; Alvarez and Franklin 1994a,b). 3Zaller (1992); Mondak (2000); Burden (2000); Berinsky (2002).


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