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Differential Item Functioning (DIF)in Terms of Gender in a High Stakes Test

Tayebi, Alireza | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: English
  3. Document No: 42133 (31)
  4. University: Sharif University of Technology
  5. Department: Languages and Linguistics Center
  6. Advisor(s): Salehi, Mohammad
  7. Abstract:
  8. Validation is an important enterprise especially when the test to be validated is a high-stakes one the results of which bring about life-changing implications for the candidates (Roever, 2001). Messick’s (1988) notion of construct irrelevant factors is pertinent in test validation. Demographic variables like gender, field of study and age can affect test results and interpretations. A fair test needs to be neutral when it comes to construct irrelevant factors such as gender. Differential Item Functioning is a way of making sure that the test does not favor one group of test takers over the others. The current study investigated differential item functioning (DIF) in terms of gender in the University of Tehran English Language Proficiency Test which is a high-stakes test using a three-step Logistic Regression procedure (Zumbo, 1999). This test is made up of three sections of grammar, vocabulary and reading comprehension comprising 100 items all of which were investigated. The participants of the study were 8,696 test takers, both males and females, who took the test in question (the UTEPT) as a partial requirement for entering a PhD program at the University of Tehran in 2007. In order to show whether the items of the UTEPT exhibited DIF or not, Logistic Regression using a three step procedure (Zumbo, 1999) was employed. Three sets of criteria were selected namely; Cohen's (1988), Zumbo's (1999), and Jodin and Gierl's (2001) in order for the results of the analyses to be checked against them. It was revealed that, though the items of the UTEPT show "small" effect sizes according to Cohen's classification, they do not display DIF based on the other two criteria. By implication this finding indicates that, the UTEPT has been made so flawlessly due to its not having any adverse force on gender groups. Therefore, it can be concluded that the test in question favors neither males nor
    females who take it.
  9. Keywords:
  10. Validity ; Test Validation ; Test Fairness ; Differential Item Functioning (DIF) ; Logistic Regression (LR)Analysis

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