Abstract

The purpose of this study is to carry out differential item functioning (DIF) analysis for content areas of a reading comprehension subtest using four area indices within Item Response Theory (IRT) framework. The differences in the magnitudes of the area indices were compared based on the subject areas. The DIF analysis was carried out across gender groups only. The item level data of the English reading comprehension subtest were gathered from English Language Achievement exam done in School of Foreign Languages, Ege University, Turkey, in 2013. A sample of 2,117 examinees (1,011 males and 1,116 females) was randomly selected. For the DIF analysis, (a) an IRT model for the item characteristic curves was specified; (b) model-data-fit was investigated for the selected IRT model;(c) Item characteristic curves were separately computed for each group on a common scale; finally, (d) indices indicating the degree of DIF on each item were computed. The results of the study indicated that both un-weighted and weighted area indices showed non-uniformity in DIF in the item characteristic curves in reading comprehension subtest in most cases. A significant correlation was observed between un-weighted and weighted area indices.

Key words: Item characteristic curve, item bias, differential item functioning (DIF).