Differential Item Functioning: An Examination of the NEO-FFI by Sex in Older Adults

Understanding sex differences when assessing personality in older adults is important for researchers and clinicians. The current study utilized differential item functioning (DIF) to compare male and female older adults’ responses on the NEO-FFI to detect potential sources of measurement bias. Participants included 244 older adults (98 males, 146 females, mean age = 73). DIF by sex was determined using ordinal logistic regression and item response theory.Non-uniform DIF was present in item 31, and uniform DIF was present in item 26 in the Neuroticism scale. In the Extraversion scale, non-uniform DIF was present in items 32 and 37. In the Openness scale, non-uniform DIF was present in items 23 and 48; uniform DIF was present in items 53 and 58. Following Monte Carlo simulations to prevent overidentification, non-uniform DIF was present in item 31 in the Neuroticism scale and item 32 in the Extraversion scale. Results suggest that the NEO-FFI is a minimally biased measurement tool based on sex.