Using Z and age-equivalent scores to address WISC-IV floor effects for children with intellectual disability

E. Toffalini, S. Buono, T. Zagaria, A. Calcagnì, C. Cornoldi

Research output: Contribution to journalArticlepeer-review

Abstract

Background: The Wechsler Intelligence Scale for Children – Fourth Edition often produces floor effects in individuals with intellectual disability. Calculating respondents' Z or age-equivalent scores has been claimed to remedy this problem. Method: The present study applied these methods to the Wechsler Intelligence Scale for Children – Fourth Edition scores of 198 individuals diagnosed with intellectual disability. Confirmatory factor analysis and profile analysis were conducted using a Bayesian approach. Results: The intelligence structure in intellectual disability resembled the one previously reported for typical development, suggesting configural but not metric invariance. When Z or age-equivalent scores (but not traditional scaled scores) were used, the average profile resembled the one previously reported for other neurodevelopmental disorders. Conclusions: Both methods avoided any floor effects, generating similar but not identical profiles. Despite some practical and conceptual limitations, age-equivalent scores may be easier to interpret. This was true even for a subgroup of individuals with more severe disabilities (mean IQ < 43).

Original languageEnglish
JournalJournal of Intellectual Disability Research
DOIs
Publication statusAccepted/In press - Jan 1 2019

Keywords

  • floor effect
  • intellectual disability
  • intelligence
  • WISC-IV

ASJC Scopus subject areas

  • Rehabilitation
  • Arts and Humanities (miscellaneous)
  • Neurology
  • Clinical Neurology
  • Psychiatry and Mental health

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