Background: Self-determination is a psychological construct that applies to both the general population and to individuals with disabilities that can be self-determined with adequate accommodations and opportunities. As the relevance of self-determination-related skills in life has been recently acknowledged, researchers have created a measure to assess self-determination in adolescents and young adults with and without disabilities. The Self-Determination Inventory: Student Report (Spanish interim version) is empirically being validated into Spanish.
Aims: As this scale is the first assessment addressed to all youth, further exploration of its psychometric properties is required to ensure the reliability of the self-determination measurement and gain further insight into the construct when applied to youth with and without disabilities.
Methods: More than 600 participants were asked to complete the scale. The impact of disability on the item response distributions across the dimensions of self-determination was explored.
Outcomes: Differential item functioning (DIF) was found in only 5 of the scale's 45 items. Differences primary favored youth without disabilities.
Conclusions: The weak presence of DIF across the items supports the instrument's psychometrical robustness when measuring self-determination in youth with and without disabilities and provides further understanding of the self-determination construct. Implications and future research directions are also discussed.
Keywords: Causal agency theory; Differential item functioning; Self-Determination Inventory.
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