Arc’s Self-Determination Scale

Mixed Disabilities: (Wehmeyer, 1995; n = 500; Mean Age = 17.08 (1.99) years; no disability n=50; learning disability n=160; emotional disorder n=15; intellectual disability n=128; orthopedic n=1; other impairment n=6; autism n=2; speech Impairment n=2 )

• No Disability: mean score = 106.58 (SD = 15.67)
• Learning Disability: mean score = 101.87 (SD = 16.04)
• Intellectual Disability: mean score = 89.02 (SD = 21.92)

Mixed Disabilities: (Almqvist & Granlund, 2005; n = 472, Children Group Mean Age =10.04 (1.56); Youth Group Mean Age = 14.99 (1.51); Swedish sample)

• Excellent: Cronbach's alpha range from 0.82- 0.93 for children and adolescents age 7-17 in autonomy indexes*
• Poor: Cronbach’s alpha range from 0.57- 0.69 for children and adolescents age 7-17 in locus of control indexes.

Mixed Disabilities: (Wehmeyer, 1995)

• Excellent: Cronbach's alpha is 0.90 for the entire scale and 0.90 for the autonomy domain*
• Adequate: Cronbach’s alpha range is 0.73 for the psychological empowerment domain.
• Poor: Cronbach’s alpha is 0.62 for the self-realization domain.

*Scores higher than .9 may indicate redundancy in the scale questions. 

Concurrent validity:

Mixed Disabilities: (Wehmeyer, 1995)

• Adequate concurrent validity of the Self-Regulation domain using  Adult version of the Nowicki-Strickland Internal-External Scale (ANS-IE) (r = -0.32); Psychological Empowerment domain using ANS-IE,  Intellectual Achievement Responsibility Scale (IARQ), and Self-Efficacy for Social Interactions Scale (SES) (r = -0.35, 0.36, 0.47 respectively); and Self-Realization domain using SES (r = 0.37), and Total Self-Determination Scale using SES (r = 0.39).
• Poor concurrent validity for Autonomy domain using the ANS-IE, IARQ, and SES (r== -0.16, 0.20 respectively); Self-Regulation domain using the IARQ and SES (r= 0.28, 0.29, respectively); Self-Realization domain using the ANS-IE and IARQ (r=-0.27, 0.27, respectively), and Total Self-Determination score using the ANS-IE and IARQ (r=-0.26, 029, respectively).

Mixed Disabilities: (Wehmeyer, 1995)

• Use of regression analysis showed expected differentiation due to differences in age - older students did better than younger students.
• Use of regression analysis showed adequate differentiation between students with learning disabilities, students with intellectual disabilities, and students without disabilities.
• Factor analysis identified 5 factors in the autonomy domain, 3 factors within the psychological empowerment domain, and 2 factors in the self-realization domain.

Autism Spectrum Disorder: (Chou et al., 2017; n=95, Female Mean Age=17.44 (2.72); Male Mean Age=16.60(1.97))

• Excellent: Cronbach’s alpha subset ranges from 0.69 to 0.90 with an overall Cronbach’s alpha of 0.90.

Convergent Validity:

Mild Intellectual Disability: (Lachapelle et al., 2005)

• Adequate convergent validity of the ARC’s Self-Determination Scale at using the Quality of Life Questionnaire (r=0.49)

Discriminative Validity:

Autism Spectrum Disorder: (Chou et al., 2017) 

• Adequate discriminant validity. Factor correlations of four factors of SDS (autonomy, self-regulation, psychological empowerment, and self-realization) were less than 0.85. Likelihood-ratio test between the ARC’s Self-Determination Scale and the American Institutes for Research Self-Determination Scale (AIR) was significant (p<0.01) suggesting that the two tests measure distinct domains of self-determination in students with ASD.

Mild Intellectual Disability: (Lachapelle et al., 2005)

• Discriminant analysis showed that the ARC’s Self-Determination Scale distinguished the high quality of life group from the low quality of life group.

Factor Analysis:

Autism Spectrum Disorder: (Chou et al., 2017)

• Confirmatory factor analysis of the ARC’s Self-Determination Scale supported the hypothesized structure for the Autonomy and Self-Regulation subscales, and generally for the Psychological Empowerment and Self-Realization subscales, with some problematic areas that warrants future research. 

Intellectual Disability: (Wehmeyer & Bolding, 1999)

• Factor analysis identified 9 factors: 4 domains of autonomy, 3 domains of psychological empowerment, and 2 domains of self-realization (self-regulation was not included in the test) suggesting the domains.

Intellectual Disability: (Seo et al., 2013)

• Confirmatory factor analysis showed that the four subdomains (i.e., autonomy, self-regulation, psychological empowerment, and self-realization) were invariant across students with emotional/behavioral disorders and students with learning disabilities.