Reliability of the SKILLS Language Index

By Marlena N. Smith

A recent study conducted by CARD research and Development faculty found the Shaping Knowledge though Individualized Life Learning Systems (SKILLS) Language Index to have strong reliability. While early intensive behavioral intervention (EIBI) is a highly supported treatment for children with autism spectrum disorders (ASD), treatment content can differ across EIBI programs. Furthermore, assessment tools designed to identify individualized content for EIBI programs are limited, and none have undergone psychometric evaluation. The purpose of this study was to evaluate the reliability of the SKILLS Language Index.

The SKILLS Index is a comprehensive assessment instrument developed to identify appropriate treatment content for EIBI programs. While the SKILLS Index covers all areas of human functioning, this study focused specifically on the SKILLS Language Index. To learn more about SKILLS and the SKILLS Index visit

This study evaluated the reliability of the SKILLS Language Index. Reliability measures an instrument’s ability to replicate results over time (test-retest reliability) or between raters (inter-rater reliability). Participants included 66 children who were randomly selected from a pool of over 1000 children with ASD. Two therapists completed the SKILLS Language Index for each participant within a one week period. Additionally, one therapist completed the SKILLS Language Index twice within a one month period.

The SKILLS Language Index was found to have excellent internal consistency, test-retest reliability, and inter-rater reliability. Furthermore, the SKILLS Language Index is the first assessment directly linked to an ABA curriculum for children with ASD to receive psychometric research. While this study found the SKILLS Language Index to have strong reliability, further research is needed to evaluate the reliability of the other domains within the SKILLS Index in addition to the validity of the entire instrument.

The CARD research team would like to thank the more than 100 therapists that assisted with the study, and particularly Catherine Peters for her help coordinating the project.


Dixon, D. R., Tarbox, J., Najdowski, A. C., Wilke, A. E., & Granpeesheh, D. (in press). A
comprehensive evaluation of language for early behavioral intervention programs: The reliability
of the SKILLS Language Index. Research in Autism Spectrum Disorders.

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