Rating of Psychometric characteristics of Gilliam Scale (GARS-3) for Evaluation of Autism Spectrum Disorder in Libyan Environment

Abstract

The research aimed to evaluate the psychometric characteristics of the third version of the Gilliam scale for rating autism spectrum disorder in the Libyan environment. The descriptive analytical approach has been employed to reveal the psychometric characteristics of Libyan version vocabulary of the scale, calculate its stability coefficients and verify its validity indicators in measuring autism spectrum disorder. The research sample consisted of (87) individuals, including (55) males and (32) females who were randomly selected from people with mental disabilities, those with autism spectrum disorder and normal ones who frequently come to Care and Rehabilitation of Autistic Children Zliten Centre.  The ages of sample members from three categories ranged between (4.5-17.93) years. Libyan version of Gilliam scale (GARS-3), which was developed by researcher, from version that was translated by Adel Abdullah and Abeer Abu Al-Majd, and childhood autism rating scale (CARS) were considered as the main research means. The results showed that the coefficient of stability of the dimension to which the item belongs does not increase by excluding it except in six cases and most of the items’ correlation coefficients with dimensions to which they belong are statistically significant. Also, most items have high differential coefficients.  The stability coefficients of the scale dimensions computed by re-application and Cronbach’s alpha coefficient methods ranged between (0.95 - 0.71). Stability coefficients of the scale as a whole computed by the same methods were (0.87, 0.89), respectively. The results also showed that the construction validity indicators by calculating the correlation coefficients of the scale dimensions with the total score ranged between (0.57 - 0.8) and validity of the test was also verified using the CARS autism scale, so the correlation coefficient between the two scales was (0.64) which is a statistically significant value at (0.01). Finally, the results showed that the scale differentiates between contrary groups of people with autism spectrum disorder, mental disabilities and normal ones.