Psychometric Evaluation of a Big Five Personality State Scale for Intensive Longitudinal Studies.

Despite enthusiasm for using intensive longitudinal designs to measure day-to-day manifestations of personality underlying differences between people, the validity of personality state scales has yet to be established. In this study, we evaluated the psychometrics of 20-item and 10-item daily, Big Five personality state scales in three independent samples ( = 1,041). We used multilevel models to separately examine the validity of the scales for assessing personality variation at the between- and within-person levels. Results showed that a five-factor structure at both levels fits the data well, the scales had good convergent and discriminative associations with external variables, and personality states captured similar nomological nets as established global, self-report personality inventories. Limitations of the scales were identified (e.g., low reliability, low correlations with external criterion) that point to a need for more, systematic psychometric work. Our findings provide initial support for the use of personality state scales in intensive longitudinal designs to study between-person traits, within-person processes, and their interrelationship.