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Wechsler’s Definition of IQ

TM. 1. 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

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Wechsler’s Definition of IQ

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  1. TM 1

  2. 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

  3. 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 Revisions and Changes Goals of the WAIS–III 3

  4. 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 Revisions and Changes Goals of the WAIS–III 4

  5. 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

  6. Demographic Stratification Variables • Age • Sex • Race/Ethnicity • Education Level • Geographic Region 6

  7. 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

  8. 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

  9. 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

  10. WAIS–III Subtestsfor Index Scores • Vocabulary • Similarities • Information Verbal Comprehension Perceptual Organization WorkingMemory ProcessingSpeed • Picture Completion • Block Design • Matrix Reasoning • Arithmetic • Digit Span • Letter–Number Sequencing • DigitSymbol—Coding • Symbol Search 10

  11. Summary of Verbal Subtest Changes Total Items WAIS–R Unchanged or Slightly Modified Total Items WAIS–III Substantially Modified New Items Subtest Vocabulary 35 25 0 8 33 Similarities 14 11 0 8 19 Arithmetic 14 13 1 6 20 Digit Span 14 14 0 1 15 Information 29 18 1 6 18 Comprehension 16 12 0 6 18 Letter–Number Sequencing — — — 7 7 11

  12. Summary of Performance Subtest Changes Total Items WAIS–R Unchanged or Slightly Modified Total Items WAIS–III Substantially Modified New Items Subtest Picture Completion 20 8 2 15 25 Digit Symbol —Coding 93 93 0 40 133 Block Design 9 9 0 5 14 Matrix Reasoning — — — 26 28 Picture Arrangement 10 5 0 6 11 Symbol Search — — — 60 60 Object Assembly 4 3 1 2 5 12

  13. Converting Raw Scores to Scaled Scores Reference Group Scaled Scores Age-Adjusted Scaled Scores Raw Score VERBAL PERF. VC PO WM PS SUBTESTS Picture Completion Vocabulary Digit Symbol–Coding Similarities Block Design Arithmetic Matrix Reasoning 22 12 12 12 56 13 13 15 54 7 7 6 28 12 12 13 41 1 1 1 1 10 1 1 8 8 9 20 13 13 12 13

  14. Converting Sums of Scaled Scoresto IQ and Index Scores VIQ PIQ FSIQ VCI POI WMI PSI IQ/INDEX SCORES Sums of Scaled Scores IQ/Index Scores Percentiles Confidence Intervals 62 55 117 101 106 103 53 66 58 96– 99– 99– 106 112 107 95 % 14

  15. Plotting Subtest Scores (IQ) 15

  16. Plotting Subtest Scores (Index) 16

  17. Determining Strengths and Weaknesses 67 70 = 137 7 7 ÷ 14 9.57 10 9.79 Total ÷ No. of Subtests Mean Score Overall Mean Frequency of Difference in Standardization Sample Statistical Significance .05Level Scaled Score Mean Score Difference from Mean Strength(+) Weakness(–) SUBTESTS Vocabulary Similarities Arithmetic Digit Span Information Comprehension 13 9.57 3.43 2.10 5 <5% 12 9.57 2.43 2.77 8 9.57 –1.57 2.63 7 9.57 –2.57 2.40 W >25% 1 1 9.57 1.43 2.34 1 1 9.57 1.43 2.96 17

  18. Discrepancy Analysis Frequency of Difference in Standardization Sample Statistical Significance .05 Level DISCREPANCY COMPARISONS Score1 Score2 Difference Verbal IQ –Performance IQ Verbal Comprehension – Perceptual Organization Verbal Comprehension – Working Memory Perceptual Organization – Processing Speed 101 106 -5 8.48 110 111 -1 9.78 110 80 30 9.08 2.3% 111 79 32 12.13 2.6% VIQ PIQ VCI POI VCI WMI POI PSI FWD BKWD Digits Forward – Backward 7 5 2 60% 18

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