WAIS Score Comparisons and Discrepancy Analysis 2 — Questions and Answers
Question 1: The General Ability Index (GAI) is composed of which two WAIS-IV index scores?
- Verbal Comprehension Index (VCI) and Perceptual Reasoning Index (PRI) (Correct answer)
- Working Memory Index (WMI) and Processing Speed Index (PSI)
- Verbal Comprehension Index (VCI) and Working Memory Index (WMI)
- Perceptual Reasoning Index (PRI) and Processing Speed Index (PSI)
Correct answer: Verbal Comprehension Index (VCI) and Perceptual Reasoning Index (PRI)
The GAI is derived from the VCI and PRI subtests, providing an estimate of general intellectual ability that is less influenced by working memory and processing speed.
Question 2: Why is the GAI preferred over the FSIQ when an examinee has a significant discrepancy between GAI and the Cognitive Proficiency Index (CPI)?
- A large GAI–CPI discrepancy indicates that the FSIQ is not a valid unitary estimate of general intelligence (Correct answer)
- The GAI is always more reliable than the FSIQ for adults over age 65
- The CPI subtests have lower floors, making GAI a more accurate low-end estimate
- Federal law requires GAI use when processing speed scores fall below 80
Correct answer: A large GAI–CPI discrepancy indicates that the FSIQ is not a valid unitary estimate of general intelligence
When GAI and CPI differ substantially, the FSIQ blends two dissimilar cognitive profiles into one number, making it a misleading summary; the GAI better represents reasoning and knowledge in those cases.
Question 3: The Cognitive Proficiency Index (CPI) on the WAIS-IV is derived from which two index scores?
- Working Memory Index (WMI) and Processing Speed Index (PSI) (Correct answer)
- Verbal Comprehension Index (VCI) and Processing Speed Index (PSI)
- Perceptual Reasoning Index (PRI) and Working Memory Index (WMI)
- Full Scale IQ and General Ability Index (GAI)
Correct answer: Working Memory Index (WMI) and Processing Speed Index (PSI)
The CPI combines WMI and PSI to measure cognitive efficiency—how quickly and accurately an individual manipulates and processes information.
Question 4: Regression to the mean is an important consideration in WAIS-IV discrepancy analysis because:
- Predicted achievement scores derived from ability scores must account for the fact that extreme ability scores overestimate expected achievement (Correct answer)
- Index scores measured on two separate occasions will always increase due to practice effects
- Subtest scaled scores systematically inflate when the examinee is anxious
- Standard errors of measurement are larger for composite scores than for individual subtests
Correct answer: Predicted achievement scores derived from ability scores must account for the fact that extreme ability scores overestimate expected achievement
Because of imperfect test-criterion correlations, predicting achievement from an extreme ability score (very high or very low) requires adjusting toward the mean to avoid over- or under-predicting performance.
Question 5: When comparing WAIS-IV index scores in older adults (ages 65–90), clinicians must be especially cautious because:
- Normal age-related declines in PSI and WMI can make discrepancies appear clinically significant when they reflect typical aging (Correct answer)
- The WAIS-IV does not have normative data for adults over age 64
- Crystallized verbal abilities decline faster than processing speed in healthy aging
- The GAI is not calculated for examinees over age 70
Correct answer: Normal age-related declines in PSI and WMI can make discrepancies appear clinically significant when they reflect typical aging
Processing speed and working memory decline with normal aging, so a PSI or WMI that is lower than VCI may reflect typical developmental change rather than pathology in older adults.
Question 6: A clinician finds that an examinee's four WAIS-IV index scores range from 72 to 112 (a 40-point spread). The recommended interpretive approach is to:
- Interpret each index score separately rather than relying on the FSIQ as a meaningful overall summary (Correct answer)
- Average the four index scores and report only that combined figure
- Report only the lowest index score as the most valid estimate of functioning
- Discard the assessment and re-administer with an alternate battery
Correct answer: Interpret each index score separately rather than relying on the FSIQ as a meaningful overall summary
When index scores are highly variable, the FSIQ obscures important within-person differences; clinicians should interpret each index on its own merits to give an accurate picture of cognitive strengths and weaknesses.
Question 7: Which statistical concept explains why an examinee with a very high VCI is likely to show a lower PRI even without any true cognitive weakness in visuospatial reasoning?
- Regression to the mean (Correct answer)
- Standard error of measurement
- Floor effect
- Practice effect
Correct answer: Regression to the mean
Regression to the mean predicts that scores on a second, correlated measure will be less extreme than the first; a very high VCI score statistically predicts a PRI closer to the mean, even without genuine weakness.
WAIS Score Comparisons and Discrepancy Analysis 2
The General Ability Index (GAI) is composed of which two WAIS-IV index scores?