Psychometric Properties of the Vineland Adaptive Behavior Scales-Third Edition Domain-Level Teacher Form in a Sample of Pupils With Intellectual Disabilities in Germany.

BACKGROUND: Measurement of adaptive competencies is important in the assessment, educational planning and progress monitoring of children with intellectual disabilities. The responsible use of diagnostic instruments in clinical and educational settings requires a comprehensive psychometric knowledge base for all intended uses of test scores. The Vineland-3 is a widely used instrument that incorporates three dimensions of adaptive behaviour: Communication, Daily Living Skills and Socialization. Despite their widespread use, few studies have addressed the reliability of the Vineland-3 Domain-Level Teacher Form in children with intellectual disabilities. METHOD: Reliability, known-groups validity, distributional characteristics and intercorrelations of the domain scales from the German adaption of the Vineland-3 Domain-Level Teacher Form were examined in a sample of 600 pupils with intellectual disabilities. RESULTS: Reliability coefficients for the domain scales and the Adaptive Behavior Composite (ABC) were excellent (0.95-0.98), and known-groups validity was as expected, with most ABC scores (88.0%) falling below 70. The test floor of 20 (corresponding to a z score of -5.33 with an expected occurrence of approximately 1 in 20 million cases) was reached in 15.8% of the sample. Despite the assumed conceptual distinctiveness of the scales intercorrelations of domain scales were substantial (r = 0.76-0.91) in all age groups. All domain scales correlated very strongly with the ABC score (r ≥ 0.90). CONCLUSION: The German Domain-Level Teacher Form of the Vineland-3 demonstrated high reliability. However, our data strongly advise caution when interpreting standard scores in the very low range. We suggest that test publishers verify the accuracy of the norms of the Domain-Level Teacher Form.