Rehabilitation Psychology, Vol 70(2), May 2025, 131-143; doi:10.1037/rep0000564
Forber-Pratt and colleagues’ Disability Identity Development Scale (DIDS) is the only disability identity measure that meets all the criteria for rigorous scale development. Little is known however about item fit for the DIDS. Purpose/Objective: (a) To investigate the construct validity of the DIDS scores at the item and factor level using item response theory (IRT) and confirmatory factor analysis (CFA); (b) to investigate convergent validity of the DIDS scores with related constructs; and (c) to determine the reliability of each DIDS factor. Research Method/Design: A convenience sample of 210 undergraduate college students with disabilities enrolled in a west coast 4-year public university participated in this study. Measures included the DIDS, the University Belongingness Questionnaire, and the College Self-Efficacy Inventory. Data were analyzed using the Rasch IRT framework, CFA, Omega reliability, and correlational analyses. Results: IRT and CFA results revealed the data fit a 36-item, four-factor DIDS structure. Three items in the factor measuring adoption of disability community values items were easier, and four items in the factor measuring contribution to the disability community were difficult as compared with other DIDS items. Omega reliability analyses showed strong reliability for each DIDS factor. Correlation analyses found convergent and discriminant validity evidence for the DIDS with correlations with the University Belongingness Questionnaire and College Self-Efficacy Inventory in the hypothesized direction and magnitude. Conclusion/Implications: Findings provide evidence for Forber-Pratt and colleagues’ theoretically and empirically derived DIDS, advancing the research, measurement, and practical application of disability identity development. Results are aligned with Forber-Pratt’s psychosocial model of disability identity theoretical framework. (PsycInfo Database Record (c) 2025 APA, all rights reserved)