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Error in the estimation of intellectual ability in the low range using\ud the WISC-IV and WAIS-III

By Simon Whitaker


The error, both chance and systematic, in the measure of true intellectual ability in the low IQ range is quantified and combined to find an overall confidence interval. The chance error was due to: lack of stability, scorer error and lack of internal consistency. The systematic error was due to: the Flynn effect, a floor effect and that error apparent from the lack of agreement between the WISC-IV and WAIS-III. For low Full Scale IQs the WAIS-III can only be considered accurate to within 18 points above the measured IQ and 28 points below, and the WISC-IV to 16 points below the measured IQ and 25 points above it. The implications for the diagnosis of intellectual disability are considered

Topics: BF
Publisher: Elsevier
Year: 2010
OAI identifier:

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  2. (2002). American Association on Mental Retardation doi
  3. (1989). Continuing secular increases in intelligence and stable prevalence of high intelligence levels. doi
  4. (2000). Diagnostic and Statistical Manual of Mental Disorders (4th edn), Text Revision. Washington DC: doi
  5. (1986). Disparity in mental retarded persons’ IQs derived from different intelligence tests.
  6. (1966). internal consistency of the WISC with the mentally retarded.
  7. (2001). Learning Disability: Definitions and Contexts.
  8. (1997). Psychological Testing (seventh edition). Upper Saddler River: Prentice-Hall Inc Baroff,
  9. (2003). Should we abandon the concept of mild learning disability?
  10. (1972). The Dependability of behavioral measurement: Theory of Generalizability of scores and profiles. doi
  11. (2008). The distribution of scale score and possible floor effects on the WISC-III and WAIS-III. doi
  12. (2004). The end of the Flynn Effect? A study of secular trends in the mean intelligence test scores of Norwegian conscripts during the half a century. doi
  13. (2008). The stability of IQ in people with low intellectual ability: An analysis of the literature. doi
  14. (2001). Valuing People: A New Strategy for Learning Disability for the 21st Century. doi
  15. (1989). Variations in the Wechsler interscale IQ disparities at different levels of IQ. doi
  16. (1997). WAIS-III, WMS-III: Technical and Interactive Manual. doi
  17. (1981). Wechsler Adult Intelligence Scale – Revised: doi
  18. (2003). Wechsler Intelligence Scale for Children – Fourth Edition: Technical and Interactive Manual. doi
  19. (2004). Wechsler Intelligence Scale for Children – Fourth UK Edition: Administrative and Scoring Manual. doi
  20. (1974). Wechsler Intelligence Scale for Children – Revised: doi
  21. (1985). Wechsler intelligence tests: Do we really have a criterion of mental retardation?
  22. (1939). Wechsler-Bellevue Intelligence Scale. doi
  23. (2007). What is Intelligence: Beyond the Flynn Effect. Cambridge: doi

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