Bifactor Structure of the Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition

• Published in: School psychology quarterly 2014-03, Vol.29 (1), p.52-63
• Main Authors: Watkins, Marley W, Beaujean, A. Alexander
• Format: Article
• Language: English
• Subjects: Child; Child, Preschool; Children & youth; Discriminant analysis; Factor Analysis; Factor Analysis, Statistical; Factor Structure; Female; Goodness of Fit; Human; Humans; Intelligence; Intelligence Tests; Male; Models, Psychological; Preschool Children; Psychology; Psychometrics; Rating Scales; Reproducibility of Results; Robustness (Statistics); Scores; Subtests; Test Reliability; Wechsler Preschool Primary Scale; Wechsler Preschool Primary Scale of Intelligence; Wechsler Scales
• ISSN: 1045-3830; 2578-4218; 1939-1560; 2578-4226
• DOI: 10.1037/spq0000038

The Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition (WPPSI-IV; Wechsler, 2012) represents a substantial departure from its predecessor, including omission of 4 subtests, addition of 5 new subtests, and modification of the contents of the 5 retained subtests. Wechsler (2012) explicitly assumed a higher-order structure with general intelligence (g) as the second-order factor that explained all the covariation of several first-order factors but failed to consider a bifactor model. The WPPSI-IV normative sample contains 1,700 children aged 2 years and 6 months through 7 years and 7 months, bifurcated into 2 age groups: 2:6-3:11 year olds (n = 600) and 4:0-7:7 year olds (n = 1,100). This study applied confirmatory factor analysis to the WPPSI-IV normative sample data to test the fit of a bifactor model and to determine the reliability of the resulting factors. The bifactor model fit the WPPSI-IV normative sample data as well as or better than the higher-order models favored by Wechsler (2012). In the bifactor model, the general factor accounted for more variance in every subtest than did its corresponding domain-specific factor and the general factor accounted for more total and common variance than all domain-specific factors combined. Further, the domain-specific factors exhibited poor reliability independent of g (i.e., ωh coefficients of .05 to .33). These results suggest that only the general intelligence dimension was sufficiently robust and precise for clinical use.