Document Type : Research Paper
Authors
Abstract
This study aims to investigate the psychometric characteristics of specialized items of distance education psychology examinations held by Payame Noor University in 2006. To do this, 2000-subject sample was randomly selected from among all those sitting for the distance education psychology exam. Then, the sample group was randomly divided into two 1000-subject groups; one of which was used for parameter estimation, and the other for testing model-data fit. In order to analyze the test and its items based on the classical test theory (CTT), in addition to calculating frequency distribution of distracters, items variance, difficulty index, discrimination index and reliability coefficient of the test were computed. In order to analyze the test and its items based on the item- response theory (IRT), assumptions of unidimensionality and local independence were first examined. In this piece of research, in order to determine unidimensionality, all specialized psychology exams were studied in terms of factor analysis by TESTFACT Program. Results of the analyses of the above exams suggested that all of them are unidimensional, and therefore local independence assumptions are verified. Model-data fit was explored by means of BILOG-MG software, and finally, items' parameters (difficulty, discrimination and guessing) estimated along with subjects' ability parameters were extracted. Distracters' analysis showed that all items' distracters were not homogeneous in terms of probability and have had poor performance. It also indicated that in psychology and sociology exams, two-parameter model, and in philosophy exam, three- parameter model were best fit for test items. At the same time, despite the fact that mean of all exams was lower than the criterion score, it seems that the difficulties in the subject of philosophy have been more and this exam had more impact on the subjects' academic failure.
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