An Item Response Theory Analysis of the Scales from the International Personality Item Pool and the NEO Personality Inventory-Revised

Personality tests are widely used in the field of Industrial/Organizational Psychology; however, few studies have focused on their psychometric properties using Item Response Theory. This paper uses IRT to examine the test information functions (TIFs) of two personality measures: the NEO-PI-R and scales from the International Personality Item Pool. Results showed that most scales for both measures provided relatively consistent levels of information and measurement precision across levels of theta (q). Although the NEO-PI-R provided overall higher levels of information and measurement precision, the IPIP scales provided greater efficiency in that they provided more precision per item. Both scales showed substantial decrease in precision and information when response scales were dichotomized away from the original 5 point likert scale format. Implications and further avenues for research are discussed.