It comprises 10 core subtests that yield four factor index scores (i.e., Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed) as well as the full-scale IQ. The latest version of the WAIS, the fourth edition, introduced several improvements over previous editions : (1) Reduced administration time (2) updated structure to ensure compatibility with Carroll, Cattell, and Horn’s theoretical conceptualization of intelligence (3) addition of 53% new items (4) improved clinical utility and (5) revision of the subtests administered, the order of the items, a number of sample items, start-point items, stopping rule, the administration time, and bonus-point allotment. The Wechsler Adult Intelligence Scale (WAIS) is one of the most important measures developed to assess the cognitive abilities, and it has become an essential tool for a wide range of practitioners. Conclusions: Overall, the results suggest that the Egyptian WAIS-IV offers a highly valid assessment of intellectual abilities, despite the need for some improvements. Furthermore, most subtests have items that do not follow the difficulty rank they are ascribed in the WAIS-IV manual. However, each subtest included at least some items with limited ability to distinguish between individuals with differing levels of the cognitive variable being measured. Most items of the Egyptian WAIS-IV showed high discrimination, and the scale was adequately informative across the levels of latent traits (i.e., cognitive variables). Among IRT models, the two-parameter logistic model provided a good fit for dichotomous subtests, while the graded response model fitted the polytomous data. Results: Factor analysis indicated the unidimensionality of each subtest. In addition, factor analysis was performed to investigate the dimensionality of each subtest. The item-level and subtest statistical properties of the Egyptian WAIS-IV were established using a combination of four dichotomous IRT models and four polytomous IRT models. Methods: The sample consisted of 250 adults from Egypt. This study investigates item and scale properties of the Egyptian WAIS-IV using item response theory (IRT) models. Background: The Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) has been adapted to 28 different cultures and there has been considerable interest in examining its structure through exploratory and confirmatory factor analysis.
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