Factor structure of the new Scandinavian WISC-V version: Support for a five-factor model

The fifth version of Wechsler Intelligence Scale for Children is designed to measure five distinct aspects of intelligence, incorporating a new fluid reasoning index to the four indexes of the previous fourth version. Several factor analyses, however, have failed to support the fifth factor. The Scandinavian version is the only national version not showing clear superiority for the five-factor solution in the Manual. In the present study, we analyze WISC-V protocols from a clinical sample of 237 children tested with the new Scandinavian version. We perform six confirmatory factor analyses (CFA) testing three hierarchical-, two bifactor-, and one correlated candidate factor models. The study shows that the three-factor model does not fit the data, and that all four- and five-factor models showed good fit. The four-factor bifactor model was somewhat better than the five-bifactor and hierarchical models, but the correlated five-factor model was the superior model. Finding support for five-factors in a clinical sample representative of those most probable to be tested with the test, strengthen the claim that also the Scandinavian version measure a distinct fluid factor as intended by the test owners, and thus that clinicians may use the index scores as their main level of analysis. Review of previous CFAs show that the choice of statistical methods for CFA, bifactor or hierarchical/correlated, influence whether second order factor models are better than g-factor models.