title: The importance of measurement invariance in neurocognitive ability testing.
abstract: OBJECTIVE
  Neurocognitive test batteries such as recent editions of the Wechsler's Adult Intelligence Scale (WAIS-III/WAIS-IV) typically use nation-level population-based norms. The question is whether these batteries function in the same manner across different subgroups based on gender, age, educational background, socioeconomic status, ethnicity, mother tongue, or race. Here, the author argues that measurement invariance is a core issue in determining whether population-based norms are valid for different subgroups.
  
  
  METHODS
  The author introduces measurement invariance, argues why it is an important topic of study, discusses why invariance might fail in cognitive ability testing, and reviews a dozen studies of invariance of commonly used neurocognitive test batteries.
  
  
  RESULTS
  In over half of the reviewed studies, IQ batteries were not found to be measurement invariant across groups based on ethnicity, gender, educational background, cohort, or age. Apart from age and cohort, test manuals do not take such lack of invariance into account in computing full-scale IQ scores or normed domain scores.
  
  
  CONCLUSIONS
  Measurement invariance is crucial for valid use of neurocognitive tests in clinical, educational, and professional practice. The appropriateness of population-based norms to particular subgroups should depend also on whether measurement invariance holds with respect to important subgroups.
authors.affiliation: a Department of Methodology and Statistics , Tilburg University , Tilburg , The Netherlands.
authors.forename: Jelte M
authors.initials: JM
authors.lastname: Wicherts
mesh_terms: D000328:Adult; D003071:Cognition; D005006:Ethnicity / Q000523:psychology; D005260:Female; D006801:Humans; D007361:Intelligence Tests / Q000592:standards*; D008297:Male; D009483:Neuropsychological Tests / Q000592:standards*; D015203:Reproducibility of Results; D014888:Wechsler Scales / Q000592:standards
keywords: IQ tests; Measurement invariance; differential item functioning; measurement equivalence; test fairness