When Thurstone and Likert Agree—a Confounding of Methodologies

Abstract

Failure to execute Thurstone Equal-Appearing Internal Scaling procedures led to an examination of the logic of these procedures and their relationship to Likert's Summated Ratings procedures. Evidence indicated that raters frequently confound Thurstone and Likert procedures, but this error is undetectable in a large number of cases. It was further demonstrated that detection of the confounding error depends upon the referent issue and the extremes of attitude held by raters.