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

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; 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.