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. This study investigates item and scale properties of the Egyptian WAIS-IV using item response theory (IRT) models. Methods: The sample consisted of 250 adults from Egypt. 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. In addition, factor analysis was performed to investigate the dimensionality of each subtest. Results: Factor analysis indicated the unidimensionality of each subtest. Among IRT models, the two-parameter logistic model provided a good fit for dichotomous subtests, while the graded response model fitted the polytomous data. 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). However, each subtest included at least some items with limited ability to distinguish between individuals with differing levels of the cognitive variable being measured. Furthermore, most subtests have items that do not follow the difficulty rank they are ascribed in the WAIS-IV manual. Conclusions: Overall, the results suggest that the Egyptian WAIS-IV offers a highly valid assessment of intellectual abilities, despite the need for some improvements.

The Wechsler Adult Intelligence Scale–Fourth Edition (WAIS-IV) is one of the most well-known tests in the field of adult intelligence assessment. This study explores the validity of the Egyptian adaptation for the subscales of the WAIS-IV. Confirmatory factor analysis (CFA) indicated that the first-order, second-order, and bifactor models of both the five-factor Cattel–Horn–Carroll (CHC) and the four-factor structures fitted with the WAIS-IV. When the Arithmetic subscale was pathed to Perceptual Reasoning and Working Memory, the modified four first-order factor showed a better fit than any other model. Estimates of internal consistency revealed that Cronbach’s alpha was very high (.91) for the WAIS-IV scale and for four-factor structures (ranging from .81 to .95), while [Formula: see text] was low (0.61) for the WAIS-IV scale and for four-factor structures, ranging from 0.20 to 0.68. Overall, these findings provided adding evidence about the dimensionality of WAIS-IV with a new sample.

The fourth edition of the Wechsler Adult Intelligence Scale (WAIS-IV) has been used extensively for assessing adult intelligence. This study uses Mokken scale analysis to investigate the psychometric proprieties of WAIS-IV subtests adapted for the Egyptian population in a sample of 250 adults between 18 and 25 years of age. The monotone homogeneity model and the double monotonicity model were consistent with the subtest data. The items of all subtests except Matrix Reasoning, Information, Similarities, and Vocabulary formed a unidimensional scale. The WAIS-IV subtests have discriminatory and invariantly ordered items, although some items violated the invariant item ordering and scalability criteria. Therefore, the WAIS-IV subtests—with the exception of some items—are hierarchical scales that allow items to be ordered according to difficulty and subjects to be ordered using the sum score. In conclusion, the current study provides evidence of the dimensionality and hierarchy of the WAIS-IV subtests in the framework of Mokken scaling, although care should be taken when interpreting or including certain items.