Some EPI Reliability Estimates

The stability of the EPI over one month was estimated with 80 American university students, separately by sex (40 males, 40 females). The estimates for the extraversion-introversion (E-I), neuroticism (N) and lie scales ranged from 0.50 to 0.87. Reliability data (alternate-forms) from other sources were compared to the present results. It was concluded that the EPI has demonstrated generally high reliability for a personality measure, with reservations where the lie scale is concerned, and that the E-I scale alternate-forms, but not test-retest, reliability was generally lower than that for the N scale, suggesting that the alternate-forms are somewhat more equivalent for N than for E-I.