Employment Related Self-Determination: Construct Validation Through Psychometric Evaluation of the Vocational Fit Assessment.

Self-determination (SD) of young adults with intellectual disability (ID) is necessary to their success beyond high school, but our understanding of the construct of SD does not sufficiently invoke environmental factors or context. We explore employment-related SD of young adults with ID using psychometric methods. This cross-sectional study examines the construct validity and internal consistency of the Vocational Fit Assessment (VFA)-SD (n = 309), then concurrent validity of the VFA-SD with the Self-Determination Inventory: Parent/Teacher Report (SDI-PTR; n = 233). Ordinal exploratory factor analysis strongly suggests that VFA-SD items measure one unidimensional construct. The mean inter-item correlation was 0.61, ordinal α = 0.97, and McDonald's ω = 0.87. The VFA-SD and the SDI-PTR were positively and moderately correlated, R = 0.61, p < .001. Taken together, these complementary psychometric results validate the use of the VFA-SD but also indicate potential benefits of item refinement and the opportunity to align with widely accepted Causal Agency Theory. This work highlights the critical need for all transition professionals to consider the context when selecting appropriate assessments to measure young adults' SD, as well as the need for future research that considers employment as a relevant contextual factor.