1 / 33

Intelligence testing: A matter of life and death?

Intelligence testing: A matter of life and death?. Chad W. Buckendahl Buros Center for Testing University of Nebraska, Lincoln. Buros Center for Testing. Oscar K. Buros, 1935; UNL, 1979 Improve the science and practice of testing

sumana
Download Presentation

Intelligence testing: A matter of life and death?

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Intelligence testing: A matter of life and death? Chad W. Buckendahl Buros Center for Testing University of Nebraska, Lincoln

  2. Buros Center for Testing • Oscar K. Buros, 1935; UNL, 1979 • Improve the science and practice of testing • Buros Institute of Mental Measurements (BIMM): commercially available tests • Mental Measurements Yearbook (MMY) • Test in Print (TIP) • Buros Institute for Assessment Consultation and Outreach (BIACO): proprietary tests • Psychometric services for educational licensure, certification, admissions, and employment testing

  3. Case Background • Defendant (Erick Vela) participated in a bank robbery in Norfolk, NE in September, 2002 • Five people were killed during the robbery • One of four defendants convicted • Motion asserting mental retardation

  4. Legal Background • Atkins v. Virginia (2002) • Prohibited execution of persons with mental retardation • Additional Nebraska statute • “An intelligence quotient of 70 or below on a reliably administered intelligence quotient test shall be presumptive evidence of mental retardation.”

  5. Diagnosing Mental Retardation • Relies on multiple criteria • American Psychiatric Association and American Association of Mental Retardation: • Sub-average intellectual functioning, • Significant limitations in adaptive skills such as communications, self-care, and self-direction, and • Manifest before age of 18

  6. Defining primary criteria • Sub-average intelligence: • IQ 70 or below (2 std. dev. below mean) • Considers measurement error • Adaptive functioning: • Coping with common life demands • Standards of personal independence • Socio-cultural background • Community setting

  7. Intelligence tests • Tests administered by three different defense experts: • Wechsler Abbreviated Scale of Intelligence (WASI): July 2003 • Wechsler Adult Intelligence Scales (3rd ed.) (WAIS-III): November 2003 • Stanford-Binet (5th ed.) (SB5): July 2004

  8. Adaptive Behavior Tests • July 2003: none • November/December 2003: none • 2004-05: Vineland Adaptive Behavior Scales • Defense: defendant’s sister • State: two friends of the defendant

  9. Malingering tests • Administered when there are concerns about motivation/effort in performance • July, 2003: none • November, 2003: • Test of Memory Malingering (TOMM) • Victoria Symptom Validity Test (VSVT) • Validity Indicator Profile (VIP) • 21-item test • July, 2004: none

  10. Professional Standards • Standards for Educational and Psychological Testing (AERA, APA, & NCME, 1999) • Validity • Reliability • Administration • Scoring • Score Interpretation

  11. Validity Argument • “Ultimately, the validity of an intended interpretation of test scores relies on all the available evidence relevant to the technical quality of a testing system. This includes . . .appropriate test administration and scoring. . .” (Standards, p. 17)

  12. Administration and Scoring • “The usefulness and interpretability of test scores require that a test be administered and scored according to the developer’s instructions. . . Without such standardization, the accuracy and comparability of score interpretations would be reduced.” (Standards, p. 61)

  13. Scores • WASI: 87 (Full Scale IQ) • 82 (Verbal IQ), 94 (Performance IQ) • WAIS-III: 75 (FSIQ) • 75 (VIQ), 78 (PIQ) • SB5: 66 (FSIQ) • 56 (VIQ), 79 (Nonverbal IQ)

  14. Interpreting scale scores • Full scale score relative to average (mean) score for population (i.e. 100) • Full scale score relative to the statutory cut score (i.e. 70) • Expected range of full scale and sub-scale scores given defendant’s observed scores

  15. WASI caution “[The WASI] should not be used alone to make diagnosis or educational placement decisions. It is not meant to replace more comprehensive measures of intelligence, such as the WISC-III and the WAIS-III." (Technical Manual, p.8)

  16. Interpreting WAIS-III Scores “. . .a low score on the WAIS-III does not necessarily reflect a low level of intellectual functioning. . . other factors such as the following may be implicated: cultural and linguistic discrepancy from the test’s standardization sample, disabling distractibility or anxiety, severe psychopathology, deafness, poor motivation or inadequate persistence, and extremely oppositional behavior or very poor rapport with the examiner. Before diagnosing low intellectual functioning or mental retardation, the examiner must rule out these factors.” (emphasis added) Administration and Scoring Manual (pp.7-8)

  17. SB5 VIQ/NVIQ Differences • The defendant had a… • Full scale IQ (FSIQ) score of 66 • Verbal IQ (VIQ) score of 56 • Nonverbal IQ (NVIQ) score of 79 • 23 point difference between VIQ and NVIQ • Only 1.9% of the standardization sample had a difference of 23 or more between VIQ and NVIQ

  18. Interpreting SB5 Scores “… when significant differences exist between the NVIQ and the VIQ, examiners should be cautious about evaluating FSIQ as a summary of an individual’s general ability level. . .When the context of the assessment and examinee’s background is influenced by such factors as communication disorders, learning disabilities, autism, or non-English background, the NVIQ may be a better indicator of global cognitive potential.” (emphasis added) Examiner’s Manual (p. 134)

  19. Full Scale Scores Over Time

  20. Verbal Scale Scores Over Time

  21. Nonverbal Scale Scores Over Time

  22. Summary of Intelligence Tests

  23. Adaptive Functioning Information • Vineland Adaptive Behavior Scales • School records • Course grades, remedial programs • Observations • Family members, teachers, inmates • Employment record, corrections officials

  24. Defense approach • Strict interpretation of the statute (i.e. reliably administered intelligence test) • Suggested that accuracy (validity) could be obtained without precision (reliability) • Consider the standard error in determining the range of possible true IQ scores • Suggested that observed scores across tests were different due to the Flynn effect (i.e. intergenerational influence on norm sample)

  25. Judge’s Ruling • Presumption of MR rejected • Validity of presumptive score: • 3rd intelligence test administered by defense • Probability of 66 on SB5 was remote • No malingering tests administered on it • Examiner did not follow interpretation directions in test publisher’s manual

  26. Judge’s Ruling (cont.) • Sub-average intelligence • Considered standard error • WAIS-III score met the criterion • Adaptive functioning • Preponderance of evidence did not support limitations in this area • Age of onset • NE’s statute does not specify age • Defense motion denied

  27. Future Research Questions • Measurement • Application of standard setting methodology for cut score • Validity of score interpretations given intended uses • Instrument development (e.g., content, norm sample) • Legal • Implications for future cases/legislation • Court’s application of current validity theory • Psychological • Criterion definition of mental retardation (rather than norm) • Interpretation of intelligence as unique from achievement • Stability of intelligence as a construct

More Related