Item Performance across Native Language Groups on the Iranian National University Entrance English Exam: A Nationwide Study

This paper reports on an investigation of differential item functioning (DIF) in the Iranian Undergraduate University Entrance Special English Exam (IUUESEE) across four native language groups including the Azeri, the Persian, the Kurdish, and the Luri test takers via Rasch analysis. A total sample of 14,172 participants was selected for the study. After establishing the unidimensionality and local independence of the data, the authors employed two methods to test for the DIF: (a) a t-test uniform DIF analysis, which showed that the Luri test-takers were more favored than other native language groups, and (b) nonuniform DIF analysis, which revealed that majority of nonuniform DIF instances functioned in favor of the low-ability Azeri, the low-ability Persian, the high-ability Kurdish, and the high-ability Luri test-takers. A possible explanation for native language-ability DIF was that the Luri and low-ability test-takers were more likely to venture lucky guesses. We also referred to socioeconomic status (e.g., test-wiseness), guessing, overconfidence, thoughtless errors, stem length, time, L1, and unappealing distractors as possible sources of DIF in IUUESEE.