The Use of Psychometric Scale Theory in Formulating Gilliam Scale GARS-3 for Diagnosing Autism Spectrum Disorder

The present paper aims to formulate Gilliam Scale GARS-3 for diagnosing autism spectrum disorder (ADS) according to the use of psychometric scale theory. In order to achieve the aim of the paper, the researchers have followed the scientific steps in formulating the scale and verifying the credibility of the translation via checking the accuracy and subjectivity in transferring all the thoughts of the scale. Then, an expert in Arabic language has checked the scale which consists of (58) items of six dimensions. The scale was applied to (500) students inside the governmental and the private centers and on a sample that was chosen according to the random class style includes the parents and trainers in Baghdad government. Likewise, to verify the psychometric features of the scale, three controls have been acknowledged for selecting the items. The controls are: the recognizing factor control through the use of the two extremist group style of the total score. Item credibility criterion that depends on an indicative associative relation between the score of the item and the total scores of the scale by using Pearson's associative factor. The ratio of the items saturation depending on the factor explorative analysis. The results of the analysis show that validity of all the items. The credibility of the scale has been verified by two ways, namely:The explicit credibility: through showing the instructions of the test and its items to a group of experts at the department of educational and psychological science. The construction credibility: through the explorative factor analysis: finding out the stability of the scale according to Alfa Cronbach, and the stability factor scored (0.941). In the light of the procedures followed by present paper, the researchers have reached to some recommendations and suggestions.