Confirmatory Measurement Modeling and Longitudinal Invariance of the CompACT-15: A Short-Form Assessment of Psychological Flexibility

The Comprehensive Assessment of Acceptance and Commitment Therapy Processes (CompACT; Francis et al., 2016) is a recently developed measure of psychological flexibility (PF) possessing several advantages over other measures of PF, including multidimensional assessment and relative brevity. Unfortunately, previous psychometric evaluations of the CompACT have been limited by their use of exploratory factor analysis to assess dimensionality, coefficient alpha to assess reliability, and a lack of attention to measurement equivalence in assessing change over time. The present study used confirmatory factor analysis (CFA) and item factor analysis (IFA) to examine the dimensionality, factor-specific reliability, longitudinal measurement invariance, and construct validity of the CompACT items in a longitudinal online sample of U.S. adults (N = 523). Converging evidence across CFA and IFA confirmatory latent variable measurement models provides support for the reduction of the 23-item CompACT to a 15-item short form with a more stable factor structure, acceptable reliability over large ranges of its three latent factors, and measurement equivalence of its items in assessing latent change over time. Results also support the construct validity of the CompACT-15 items based on its relations with theoretically relevant measures. Overall, the CompACT-15 appears to be a psychometrically sound instrument with the potential to contribute to research and intervention efforts.