Background. The Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) is essential to a wide range of practitioners for assessing adult intelligence (Weiss, Saklofske, Coalson, & Raiford, 2010). The WAIS-IV composes of 15 subtests (10 core and 5 supplemental) assessing the efficacy of cognitive ability in four domains (Verbal Comprehension, Perceptual Reasoning, Working Memory and Processing Speed). Abdelhamid, Gómez-Benito, Abdeltawwab, Abu Bakr and Kazem (2017) have adapted the WAIS-IV for the Egyptian population (WAIS-IV-AR). The Item Response Theory offers a family of models for assessing statistical properties of both dichotomous and polytomous data (Embretson & Reise, 2000). This study investigates both the item and scale psychometric properties of the WAIS-IV-AR subtests using the IRT models.
Methods: The sample consisted of 250 adults from Egypt, of whom 62% were female. All of the participants were aged between 18 and 24 (average 20.7 years). The IRT analysis was performed using the program IRTPRO 4 (Cai, Thissen & du Toit, 2011).
Results: The IRT analysis indicated that the two-parameter logistic model (2PLM) and the three-parameter logistic model fitted with the dichotomous WAIS-IV subtests. In addition, the Generalized Partial Credit Model and the Graded Response Model (GRM) fitted with the polytomous data. Thus, the item parameters for the WAIS-IV were estimated using only the 2PLM and GRM. Most items of the WAIS-IV subtests showed high discrimination. The information values indicated that the WAIS-IV subtests were adequately informative across a continuum of the trait measured (i.e., cognitive variables). However, each subtest included at least some items that showed limited ability to distinguish between individuals with differing levels of the cognitive variable being measured. In addition, some items do not proceed in order of difficulty in some subtests.
Conclusion: To conclude, the current study suggests preliminary calibrations of the WAIS-IV items for the Arabic population using the IRT models. Our findings showed that the WAIS-IV presents a highly valid assessment of intellectual abilities on the Arab population, despite the need for some improvements.
Abdelhamid, G. S. M., Gómez-Benito, J., Abdeltawwab, A. T. M., Abu Bakr, M. H. S., & Kazem, A. M. (2017). Hierarchical Structure of the Wechsler Adult Intelligence Scale–Fourth Edition with an Egyptian Sample. Journal of Psychoeducational Assessment, 073428291773285.
Cai, L., Thissen, D., & du Toit, S. H. C. (2011). IRTPRO for Windows [Computer software] (Version 2.1). Lincolnwood, IL: Scientific Software International.
Embretson, S. E., & Reise, S. P. (2000). Item Response Theory for Psychologists. Mahwah, N.J: Psychology Press.
Weiss, L. G., Saklofske, D. H., Coalson, D. L., & Raiford, S. E. (Eds.). (2010). WAIS-IV Clinical Use and Interpretation: Scientist-Practitioner Perspectives. San Diego, CA: Academic Press.