Validation of a revised version of the Physical Self-Inventory - Very Short form for youth with intellectual disabilities (PSI-VS-ID-R) : a Bayesian structural equation modeling approach

The objective of the current study was to investigate the psychometric properties of scores obtained on a revised version of the Physical Self-Inventory" Very Short form for youth with intellectual disabilities (PSI-VS-ID-R). A sample of 351 youth (M = 15.81 years) with mild to moderate levels of Intellectual Disabilities (ID) from Australia (N = 230) and Canada (N = 121) participated in this study. They respectively completed the English and French versions of the PSI-VS-ID-R, as well as additional measures of self-concept and physical fitness. Bayes structural equation modeling (BSEM) analyses provided support for the validity and reliability of the a priori nine-factor structure of scores obtained on the PSI-VS-ID-R. Moreover, additional BSEM analyses provided support for the comparability of responses obtained on the PSI-VS-ID-R (i.e., lack of differential item functioning or measurement equivalence) irrespective of linguistic versions and of participants' age, body-mass index, ID level, sex and frequency of sport involvement. Additionally, latent mean level differences in PSI-VS-ID-R's factors scores were also found across linguistic versions and as a function of youth's ID level and frequency of sport involvement. Finally, the convergent validity of scores on the PSI-VS-ID-R factors was supported in relation to measures of self-concept and physical fitness.