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Interpretation of the WISC-IV

Interpretation of the WISC-IV. November 8 & 10, 2004. Intro to the WISC-IV Scoring. Deviation IQ for 4 Index Scores and FSIQ: M = 100 SD = 15 Individual subtest standard scores: M = 10 SD = 3 Normative age group comparison IQs based on the 10 standard subtests

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Interpretation of the WISC-IV

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  1. Interpretation of the WISC-IV November 8 & 10, 2004

  2. Intro to the WISC-IV Scoring • Deviation IQ for 4 Index Scores and FSIQ: • M = 100 SD = 15 • Individual subtest standard scores: • M = 10 SD = 3 • Normative age group comparison • IQs based on the 10 standard subtests • IQ scores can range from 40-160 • Cannot compute index or FSIQ scores if: • 0 raw score on 2 of 3 VCI or PRI subtests • 0 raw score on both WMI or PSI subtests

  3. Subtest Substitution • Substitution permitted if there is a clinical need. For example, when a child has poor fine motor skill: • Substitute Cancellation for Coding • Substitute Picture Completion for Block Design • Substitution permitted if a subtest is spoiled due to administration error or environment interruption (e.g., fire drill). • Only 1 substitution allowed for each index and only 2 for overall IQ.

  4. Successive Level Approach to Test Interpretation • Full Scale IQ • Index Scores • Subtest Deviations within Composites • Intersubtest Score Comparisons • Intrasubtest Score Comparisons • Qualitative Analysis

  5. IQ and Index Scores • Calculate IQ and Index Scores • 95% confidence intervals (Tables A.2-A.6) • Percentile ranks (Tables A.2-A.6) • Classification: • Very Superior: > 130 • Superior: 120-129 • High Average: 110-119 • Average: 90-109 • Low Average: 80-89 • Borderline: 70-79 • Mild Mental Retardation: 55-69 • Moderate Mental Retardation: 40-54

  6. Are the Index Scores Interpretable? • Is there abnormal scatter among the VCI subtests? • 6 pts for 3 & 4 subtests; 7 points for 5 subtests • Is there abnormal scatter among the PRI subtests? • 7 points for 3 subtests; 8 points for 4 subtests If “yes,” index scores and discrepancy comparisons should be interpreted with caution.

  7. Are the Index Scores Interpretable?(continued) • Significant difference between WMI subtests (DS & LN)? • 3 points is significant, rounded from Table B.3 in the manual • 5 points is unusual & WMI is not interpretable • Significant difference between PSI subtests (Coding and SS)? • 4 points, rounded from Table B.3 in the manual • 4 points if CD<SS; 5 points if CD>SS is unusual and PSI is not interpretable

  8. Is there an unusual amount of scatter among the 10 subtests that comprise the FSIQ? Table B.6, p. 266

  9. If there is an unusual amount of scatter, interpret the index scores instead of the FSIQ

  10. Successive Level Approach to Test Interpretation • Full Scale IQ • Calculate IQ and confidence intervals. • Index Scores • Are the index scores interpretable? (scatter within an index) • Is there unusual scatter across the 10 subtests? • Comparison among the index scores • Subtest Deviations within Composites • Intersubtest Score Comparisons • Intrasubtest Score Comparisons • Qualitative Analysis

  11. Comparison of Index Scores • Are there any significant differences among index scores (Tables B-1 & B-2; Sattler A-2)? • Are any differences considered unusual (i.e., occurred in less than 10% of standardization group). • Significant differences can be described as more/less developed. • Unusual differences can be described as a true strength of weakness.

  12. Subtest Scores: Interindividual Comparisons

  13. Test Age Equivalents • Can calculate test age equivalents for each of the subtests (Table A.9). • This is useful when you want an estimate of a child’s mental age. • This is also useful when comparing across different tests that are not scaled equivalently.

  14. Subtest Deviations within Index Composites: Intraindividual comparisons • Calculate the overall mean of all subtests and subtract each subtest to define Ss and Ws • If VCI and PRI are different, calculate VCI and PRI means and compare subtests scores to the appropriate means. • Generate hypotheses based on Ss and Ws • Use protocol chart and Jean’s ability chart.

  15. Comparison of Subtest Scores: Intraindividual Comparisons • Intersubtest variability (comparisons across subtests when scatter is greater than 5 points, Sattler p. 124-131; Sattler Table A-2 (breaks down by age; Manual B-3). • Intrasubtest variability (comparison of scores within an individual subtest.

  16. Cautions of Intraindividual Comparisons • Avoid reporting that subtest scores of 8 or higher reflect a weakness. • Avoid reporting that subtests scores of 7 or lower reflect a strength. • See Sattler supplement p. 116 for examples of how to describe intraindividual comparisons.

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