Item Response Theory Likelihood Ratio Research Articles

DIF for examinees with different academic backgrounds

The purpose of the present study was to investigate differential item function (DIF) on the English subtest of the 1998 Korean National Entrance Exam for Colleges and Universities for examinees with different academic backgrounds (i.e., Humanities vs. Sciences) using the Item Response Theory (IRT) Likelihood Ratio (LR) approach. The English subtest consisted of a total of 55 items, which comprised the subscales of Listening Comprehension and Reading Comprehension. Data were fitted with a modified three parameter logistic IRT model, and DIF was detected using both the Mantel-Haenszel procedure and the IRT likelihood ratio approach. To evaluate a baseline estimate of DIF due to chance, the entire DIF detection procedure was repeated, with the sample randomly divided in half. The results of the study identified 18 DIF items with 28 DIF parameters. DIF magnitude for each studied item is also provided. Results of a preliminary content analysis are discussed in terms of the relationships between DIF directions and item content. Implications and recommendations for future research are also addressed.

Differential Item Functioning in the Wisc-III: Item Parameters for Boys and Girls in the National Standardization Sample

The Wechsler Intelligence Scale for Children–Third Edition (WISC-III) is the most widely used test of intelligence in the world. However, the manual for the WISC-III provides insufficient detail regarding the detection of differential item functioning (DIF). The WISC-III national standardization sample ( N = 2,200) was used to investigate DIF in six WISC-III subtests. After fitting two parameter logistic and graded response models to the data, items were tested for DIF using the item response theory likelihood ratio DIF detection method. Of the 151 items studied, 52 were found to function differently across groups. The magnitude of the DIF was also considered by examining (a) parameter differences between groups and (b) root mean squared probability differences. Because the scores of boys and girls may be composed of different items systematically scored as correct, their IQs cannot be assumed to have the same meaning. Further investigations of item content bias are recommended.