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The stability of IQ in people with low intellectual ability: an analysis of the literature

By Simon Whitaker


A meta-analysis of the stability of low IQ (IQ 80) was performed on IQ tests that have been\ud commonly used—tests that were derived by D. Wechsler (1949, 1955, 1974, 1981, 1991, 1997)\ud and those based on the Binet scales (L. M. Terman, 1960; L. M. Terman & Merrill, 1972). Weighted-\ud mean stability coefficients of .77 and .78 were found for Verbal IQ (V IQ) and Performance IQ\ud (P IQ) on the Wechsler tests and .82 for Full-Scale IQ (FS IQ) on both Wechsler and Binet tests,\ud for a mean test–retest interval of 2.8 years. Although the majority of FS IQs changed by less than\ud 6 points, 14% changed by 10 points or more. The author suggests that the results of IQ assessment\ud should be treated with more caution than previously thought

Topics: BF
Publisher: American Association on Intellectual and Developmental Disabilities
Year: 2008
OAI identifier:

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  7. (1970). I.Q. stability among educable mentally retarded children.
  8. (1983). Intratest and intertest reliability and stability of the WISC, WISC-R and WAIS full scale IQs in a mentally retarded population. doi
  9. (1962). IQ consistency in a group of institutionalized mental defectives over a period of 3 decades.
  10. (2001). Learning disability: Definitions and contexts. doi
  11. (2001). Longterm stability of the Wechsler Intelligences Scale for Children—Third Edition among students and disabilities.
  12. (1905). Me´thodes nouvelles pour le diagnostic du niveau intellectuel des anormaux. L’Anne´e doi
  13. (2002). Mental retardation: Definition, classification, and system of supports (10th ed.). doi
  14. (1982). Note on the constancy of the IQ.
  15. (1971). Relationship of Peabody Picture Vocabulary Test and the Wechsler Intelligence Scale for Children in an educable retarded group: A cautionary note. doi
  16. (1962). Reliability and stability of the Wechsler Intelligence Scale for Children for a group of mentally retarded boys.
  17. (1983). Reliability and stability of the WISC-R for children with below average IQs.
  18. (1970). Reliability of the Wechsler Intelligence Scale for Children in a group of mentally retarded children. doi
  19. (1962). Repeated measurement with the WISC. doi
  20. (1988). Six weeks to twenty-one years old: A longitudinal study of children with Down’s syndrome, and their families. doi
  21. (1997). Stability and change over time in cognitive level of children with delays.
  22. (1978). Stability of intelligence in the fetal alcohol syndrome: A preliminary report. doi
  23. (1981). Stability of the WISC-R for a sample of exceptional children. doi
  24. (1960). Stanford-Binet Intelligence Scales. Circle Pines, doi
  25. (1992). Statistical methods for psychologists (3rd ed.).
  26. (1973). The relationship between WISC and WAIS IQs with educable mentally retarded adolescents. doi
  27. (1957). The stability of W.I.S.C. IQs for selected children. doi
  28. (1985). Three-year stability of the WISC-R IQs for handicapped children from three racial groups. doi
  29. (1997). WAIS-III, WMS-III, technical manual. doi
  30. (1981). Wechsler Adult Intelligence Scale—Revised. doi
  31. (1955). Wechsler Adult Intelligence Scale. doi
  32. (1991). Wechsler Intelligence Scale for Children—Third edition. doi
  33. (1949). Wechsler Intelligence Scale for Children. doi
  34. (1985). Wechsler Intelligence Tests: Do we really have a criterion of mental retardation?
  35. (1939). Wechsler-Bellevue Intelligence Scale. doi
  36. (1998). WISC-III score changes for EMH students. doi
  37. (2003). WISC-IV, technical and interpretive manual.

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