en The Analysis of the Psychometric Properties of the Persian Version of the Early Life Events Scale based on the Item Response Theory and the Classical Theory of Measurement عمومى General پژوهشي Research Studies have shown that early life events affect physiological, psychological and social functioning and are related to a wide range of psychological problems in adulthood. The main objective of this study was to evaluate the psychometric properties of the Persian version of the Early Life Events Scale (ELES) based on the Item Response Theory (IRT) and the Classical Theory of Measurement in an Iranian population. The participants consisted of 400 students of universities in Tehran at all academic levels. Confirmatory and exploratory factor analyses were used to assess the construct validity of the ELES. Three factors were extracted from the exploratory factor analysis, and the confirmatory factor analysis confirmed the accuracy of the extracted factors. As the Cronbach’s alpha coefficient always underestimates the reliability value, the ordinal theta and R software were used to assess the reliability of the scale and the results showed that the scale has a good reliability. To evaluate the accuracy of the items, determine their strengths and weaknesses and ultimately assess their quality and remove inappropriate items, the scale items were analyzed based on the IRT and the Classical Theory of Measurement using MULTILOG__AWT_NOKT_COMMA__ the results showed that all the items are of a good quality in terms of threshold values (credibility), informative value and accuracy and that no items need to be changed or removed. 182 211 http://ijpb.ir/browse.php?a_code=A-10-39-135&slc_lang=en&sid=1 mohammad mehrnoosh esbati nevisandeh election دکتر مهرنوش اثباتی نویسنده مسیول 1003194753284600841 1003194753284600841 No دانشگاه الزهرا دانشگاه الزهرا mohammad roshanak khodabakhsh دکتر روشنک خدابخش 1003194753284600842 1003194753284600842 No دانشگاه الزهرا دانشگاه الزهرا mohammad abolghasem mehri nejad دکتر ابوالقاسم مهری نژاد 1003194753284600843 1003194753284600843 No دانشگاه الزهرا دانشگاه الزهرا mohammad zohreh khosravi دکتر زهره خسروی 1003194753284600844 1003194753284600844 No دانشگاه الزهرا دانشگاه الزهرا mohammad gholamreza sarami دکتر غلامرضا صرامی 1003194753284600845 1003194753284600845 No دانشگاه خوارزمی دانشگاه خوارزمی