The Relation Between Item Format and the Structure of the Eysenck Personality Inventory

A Likert seven-choice response format for per sonality inventories allows finer distinctions by sub jects than the traditional two-choice format. The Eysenck Personality Inventory was employed in the present study to test the hypothesis that use of the expanded format would result in a clearer and more accurate indication of test structure. The sub jects, volunteers in a psychology course, took the standard two-choice version of the EPI and a seven- choice version one week apart, with the order counter-balanced. A principal components analysis with a varimax rotation yielded two components for the two-choice format, clearly identifiable as Eysenck's "Neuroticism" and "Extraversion" which together accounted for 18% of the variance. The seven-choice version resulted in six components ac counting for 46% of the variance. The expanded format suggested inadequacies in the structure of the EPI, defined the factor structure more clearly, and explained a greater proportion of the variance. It thus demonstrated the apparent advantages of the multiple-response format for scale construction.