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This study examined whether the number of options in the Likert scale influences the psychological distance between categories. The most important assumption when using the Likert scale is that the psychological distance between options is equal. The authors proposed a new algorithm for calculating the scale values of options by applying item response theory and the ideas of Wakita to reveal the influence of the number of categories. Three types of questionnaires that were composed of the same items, but used different numbers of options to assess these items (specifically, 4-, 5-, and 7-point scales), were completed by 722 undergraduate students. The results indicated that the number of options influenced the psychological distance between options, particularly for the 7-point scale. This influence was revealed only by the authors’ algorithm; descriptive statistics and coefficients of reliability did not show that the number of options had a prominent influence. The importance of the number of options and the new algorithm are discussed.
Wakita et al. (Thu,) studied this question.