Differential Item Functioning in English Language Test Using Item Response Theory for Ethnic Groups

The study investigated detecting differential item functioning using item response theory in West African Senior School Certificate English language test in South-South Nigeria. Four research questions and one hypothesis were formulated to guide the study. Descriptive research survey design was employed for the study. The population of the study was 117845 Senior Secondary 3 students in Edo, Delta, Rivers and Bayelsa states. A sample of 1309 (604 males, 705 females) drawn through multi stage sampling technique was used for the study. One valid instrument titled: WASSCE/SSCE English language objective test (ELOT) was used to collect data for the study. The reliability index of the instrument was estimated using Richard Kuderson 20 with coefficient value of .84 for the English Language objective test Chi square and Lord Wald test statistics statistical technique employed by Item Response Theory for Patient Reported Outcome (IRTPRO) was the technique used in data analysis which provided answers to the research questions and Chi Square test to test the hypothesis at.05 level of significance. On analysis, the result revealed that significantly between Ijaw, and Bini, 20 items were flagged as exhibiting DIF, between Esan and Ijaw, 20 items showed DIF, between Isoko and Ijaw, 15 items showed DIF, between Urhobo and Ijaw, 12 items were flagged as showing DIF and the number of items that function differently was significantly dependent on ethnic groups. This thus shows a total of 95% based on ethnicity indicating large DIF and items that are potentially biased. Based on the findings recommendation were made and one among others was that Item Response theory should be used as DIF detection method by large scale public examination and test developers. Keywords; Differential item functioning, Item Response Theory, Ethnicity, English language, Examination DOI: 10.7176/JESD/10-6-02 Publication date:March 31st 201