Assessing meaningful within-person variability in Likert-scale rated personality descriptions: An IRT tree approach

• Main Authors: LANG, Jonas W. B., LIEVENS, Filip, DE FRUYT, Filip, ZETTLER, Ingo, TACKETT, Jennifer L.
• Format: text
• Language: English
• Published: Institutional Knowledge at Singapore Management University 2019
• Subjects: Variability; flux; adaptability; psychometrics; tree models; Psychology
• Online Access: https://ink.library.smu.edu.sg/lkcsb_research/6424; https://ink.library.smu.edu.sg/context/lkcsb_research/article/7423/viewcontent/assessing_meaningful_within_person__1_.pdf
• Institution: Singapore Management University

Personality researchers and clinical psychologists have long been interested in withinperson variability in a given personality trait. Two critical methodological challenges that stymie current research on within-person variability are separating meaningful within-person variability from 1) true differences in trait level and 2) careless responding (or person unreliability). To partly avoid these issues, personality researchers commonly only study within-person variability in personality states over time using the standard deviation (SD) across repeated measurements of the same items (typically across days)—a relatively resource-intensive approach. In this article, we detail an approach that allows researchers to measure another type of within-person variability. The described approach utilizes IRT on the basis of Böckenholt’s (2012) threeprocess model, and extracts a meaningful variability score from Likert-ratings of personality descriptions that is distinct from directional (trait) responding. Two studies (N = 577; N = 120- 235) suggest that IRT variability generalizes across traits, has high split-half reliability, is not highly correlated with established indices of IRT person unreliability for directional trait responding, and correlates with within-person SDs from personality inventories and withinperson SDs in a diary study with repeated measurements across days 20 months later. The implications and usefulness of IRT variability from personality descriptions as a conceptually clarified, efficient, and feasible assessment of within-person variability in personality ratings are discussed.