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Wechsler’s Definition of IQ
“Intelligence is the aggregate or global capacity of the individual to act purposefully, to think rationally and to deal effectively with his environment.” Global because it characterizes individual’s behavior as a whole Aggregate because it is composed of elements or abilities that are qualitatively differentiable Wechsler, 1939 2
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Revisions and Changes Goals of the WAIS–III
Goal 1: Continuity and Familiarity Goal 2: Updating of Norms Goal 3: Extension of Age Range Goal 4: Age-Corrected Norms Goal 5: Improved Item Content Goal 6: Improved Stimulus Materials 3
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Revisions and Changes Goals of the WAIS–III
Goal 7: Improved Diagnostic and Descriptive Utility Goal 8: De-emphasis on Performance Speed Goal 9: Enhancement of Fluid Reasoning Assessment Goal 10: Linkage with WMS–III and WIAT Goal 11: Extensive Validity Studies Goal 12: Enhancement of Scoring Rules 4
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Basic Description of the WAIS–III
Goal 1: Continuity and Familiarity Basic Description of the WAIS–III Individual Administration Assessment of Cognitive Functioning in Adults, Aged 16–89 Years Scale Composition 11 Subtests to Obtain IQ Scores 11 Subtests to Obtain Index Scores New Subtests: Matrix Reasoning, Symbol Search, Letter–Number Sequencing Optional Subtest: Object Assembly 5
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Demographic Stratification Variables
Age Sex Race/Ethnicity Education Level Geographic Region 6
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Stratification Variables: Age
16–17 18–19 20–24 25–29 30–34 35–44 45–54 55–64 65–69 45-54 70–74 75–79 80–84 85– 89 WAIS–III 200 200 200 200 200 200 200 200 200 200 200 150 100 WMS–III 100 100 100 100 100 100 100 100 100 100 100 75 75 7
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WAIS–III Levels of Performance
Structure of the Scale WAIS–III Levels of Performance FSIQ VIQ PIQ VCI WMI POI PSI Vocabulary Similarities Information Comprehension Digit Span Arithmetic Letter–Number Sequencing Block Design Matrix Reasoning Picture Completion Picture Arrangement Digit Symbol—Coding Symbol Search 8
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WAIS–III Subtests for IQ Scores
Verbal Performance Vocabulary Similarities Arithmetic Digit Span Information Comprehension Picture Completion Digit Symbol—Coding Block Design Matrix Reasoning Picture Arrangement 9
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WAIS–III Subtests for Index Scores
Verbal Comprehension Perceptual Organization Working Memory Processing Speed Vocabulary Similarities Information Picture Completion Block Design Matrix Reasoning Arithmetic Digit Span Letter–Number Sequencing Digit Symbol—Coding Symbol Search 10
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Summary of Verbal Subtest Changes
Total Items WAIS–R Unchanged or Slightly Modified Total Items WAIS–III Substantially Modified New Items Subtest Vocabulary Similarities Arithmetic Digit Span Information Comprehension Letter–Number Sequencing — — — 7 7 11
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Summary of Performance Subtest Changes
Total Items WAIS–R Unchanged or Slightly Modified Total Items WAIS–III Substantially Modified New Items Subtest Picture Completion Digit Symbol —Coding Block Design Matrix Reasoning — — — Picture Arrangement Symbol Search — — — Object Assembly 12
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Converting Raw Scores to Scaled Scores
Age-Adjusted Scaled Scores Reference Group Scaled Scores Raw Score SUBTESTS VERBAL PERF. VC PO WM PS Picture Completion Vocabulary Digit Symbol–Coding Similarities Block Design Arithmetic Matrix Reasoning 13
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Converting Sums of Scaled Scores to IQ and Index Scores
VIQ PIQ FSIQ VCI POI WMI PSI IQ/INDEX SCORES Sums of Scaled Scores IQ/Index Scores Percentiles Confidence Intervals 96– 99– 99– 95 % 14
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Plotting Subtest Scores (IQ)
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Plotting Subtest Scores (Index)
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Determining Strengths and Weaknesses
Total ÷ No. of Subtests Mean Score 67 70 = 137 7 7 ÷ 14 Overall Mean Frequency of Difference in Standardization Sample Statistical Significance .05 Level Scaled Score Mean Score Difference from Mean Strength (+) Weakness (–) SUBTESTS Vocabulary Similarities Arithmetic Digit Span Information Comprehension <5% – – W >25% 17
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Discrepancy Analysis DISCREPANCY COMPARISONS Score 1 Score 2
Frequency of Difference in Standardization Sample Statistical Significance .05 Level DISCREPANCY COMPARISONS Score 1 Score 2 Difference Verbal IQ – Performance IQ Verbal Comprehension – Perceptual Organization Verbal Comprehension – Working Memory Perceptual Organization – Processing Speed VIQ PIQ VCI POI VCI WMI POI PSI % % Digits Forward – Backward FWD BKWD % 18
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