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Response Interpolation and Scale Sensitivity: Evidence Against 5-Point Scales

Kraig Finstad

Journal of Usability Studies, Volume 5, Issue 3, May 2010, pp. 104 - 110

Article Contents


Conclusion

Taken as a whole, the case for 5-point Likert items has been further weakened. It has been found that they provided too coarse an estimate of moderator effects (Russell & Bobko, 1992), and they were outperformed consistently by 7-point Likert items in objective rank matches and subjective evaluations (Diefenbach, Weinstein, & O’Reilly, 1993). This study has shown that 5-point items were more likely than 7-point items to elicit attempts to violate the prescribed boundaries of an item, a behavioral expression of the frustration noted by Osgood, Suci, and Tannenbaum (1957). Consequently the 5-point items were more prone to contribute to inaccurate measures through subtle but repeated data loss, especially when utilized in an electronic, non-moderated format. Seven-point Likert items have been shown to be more accurate, easier to use, and a better reflection of a respondent’s true evaluation. In light of all these advantages, even when compared to higher-order items, 7-point items appear to be the best solution for questionnaires such as those used in usability evaluations. Whether usability practitioners are developing a new summative scale, a satisfaction survey, or a simple one-item post-test evaluation item it would serve them well to use a 7-point rather than a 5-point scale.

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