Validity Issues in the Likert and Thurstone Approaches to Attitude Measurement

Abstract

This article highlights the theoretical differences between the Likert and Thurstone approaches to attitude measurement and demonstrates how such differences can lead to discrepant attitude estimates for individuals with the most extreme opinions. Both simulated data and real data on attitude toward abortion are used to demonstrate this discrepancy. The results suggest that attitude researchers should, at the very least, devote more attention to the empirical response characteristics of items on a Likert attitude questionnaire. At most, these results suggest that other methods, such as the Thurstone technique or one of its recently developed item response theory counterparts, should be used to derive attitude estimates from disagree-agree responses.Introductory texts often portray the Thurstone (1928) and the Likert (1932) approaches to attitude measurement as though both methods provide equally valid scores measuring attitude when individuals respond to a set of questionnaire items using a (binary or graded) disagree-agree response scale (Mueller, 1986;Petty & Cacioppo, 1981). This overly simplistic portrayal is fostered by studies that indicate that Likert and Thurstone attitude scores typically are correlated to at least a moderate degree (.60 ≤ r ≤ .95), regardless of whether responses to the same set of items are scored with the two proce-

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