WPPSI - Wechsler Preschool and Primary Scale of Intelligence Psychometric Properties and Norms Questions and Answers — Questions and Answers
Question 1: An examiner notes that the WPPSI-IV Full Scale IQ (FSIQ) has an average internal consistency reliability coefficient of .95. This value indicates which of the following about the FSIQ score?
- The score is a valid measure of a child's true intellectual potential.
- The score is highly consistent and has a low degree of measurement error. (Correct answer)
- The score is directly comparable to achievement test scores.
- The score accurately reflects the performance of the U.S. preschool population.
Correct answer: The score is highly consistent and has a low degree of measurement error.
Reliability refers to the consistency of a measure. A high internal consistency coefficient, such as .95, indicates that the items on the test are highly intercorrelated and measure the same construct consistently. This leads to a low standard error of measurement, meaning the obtained score is likely very close to the true score.
Question 2: The WPPSI-IV standardization sample was stratified to match the 2010 U.S. Census data. Which set of variables was essential for creating this nationally representative normative group?
- The child's preschool enrollment status, family income, and number of siblings.
- The child's primary language, parental marital status, and urban vs. rural residence.
- Age, sex, race/ethnicity, parent education level, and geographic region. (Correct answer)
- The child's history of developmental milestones and parent's occupation.
Correct answer: Age, sex, race/ethnicity, parent education level, and geographic region.
The WPPSI-IV normative sample of 1,700 children was carefully selected using a stratified proportional sampling method based on key demographic variables to ensure it was representative of the U.S. population. These variables included age, sex, race/ethnicity, parent education level (as a proxy for socioeconomic status), and geographic region.
Question 3: A child obtains a Visual Spatial Index (VSI) score of 105. The examiner uses the standard error of measurement (SEM) to construct a 95% confidence interval of 97-113 around this score. What is the correct interpretation of this interval?
- There is a 95% chance the child will score between 97 and 113 on any future intelligence test.
- The child's visual spatial skills are 95% better than their peers.
- One can be 95% confident that the child's true score for the VSI falls within the range of 97 to 113. (Correct answer)
- The test is 95% valid for measuring this child's visual-spatial ability.
Correct answer: One can be 95% confident that the child's true score for the VSI falls within the range of 97 to 113.
A confidence interval provides a range of scores that likely contains the individual's 'true' score, which is the hypothetical score they would receive if there were no measurement error. The 95% confidence level means that if the child were tested 100 times, their true score would be expected to fall within the calculated range on 95 of those occasions.
Question 4: The WPPSI-IV Technical and Interpretive Manual reports studies showing that children diagnosed with an Intellectual Disability score significantly lower on the FSIQ than typically developing children. This finding provides strong evidence for the test's:
- test-retest reliability.
- content validity.
- internal consistency.
- clinical utility and construct validity. (Correct answer)
Correct answer: clinical utility and construct validity.
This is an example of a special group study, which is used to establish construct validity and demonstrate the test's clinical utility. By showing that the test can differentiate between a clinical group (Intellectual Disability) and a matched control group in a theoretically expected direction, it supports the claim that the test is measuring the construct of intelligence and is useful for clinical diagnosis.
Question 5: A psychologist is reviewing the test-retest reliability coefficients for the WPPSI-IV index scores over a short interval (e.g., 2-4 weeks). Which of the following is most likely to be true regarding these stability coefficients?
- The FSIQ will have lower stability than any of the individual index scores.
- All index scores will have stability coefficients above .95.
- The FSIQ will generally have the highest stability, followed by the primary index scores. (Correct answer)
- The stability of scores is expected to be perfect, with a coefficient of 1.0.
Correct answer: The FSIQ will generally have the highest stability, followed by the primary index scores.
In psychometrics, composite scores derived from more items (like the FSIQ) are almost always more reliable than the shorter scales that contribute to them. Short-term test-retest stability coefficients for the WPPSI-IV FSIQ are very high (around .88-.93), while the index scores are also strong but typically slightly lower (e.g., .78-.88).
Question 6: To determine if the difference between a child's Verbal Comprehension Index (VCI) of 112 and their Processing Speed Index (PSI) of 95 is statistically significant, an examiner should compare the 17-point difference to the:
- child's overall FSIQ score.
- standard deviation of the two index scores.
- critical value provided in the manual's statistical tables. (Correct answer)
- average score difference found in the child's grade level.
Correct answer: critical value provided in the manual's statistical tables.
The WPPSI-IV manuals provide statistical tables with critical values for determining the significance of differences between index scores. An obtained difference is considered statistically significant if it meets or exceeds the critical value at a chosen level of confidence (e.g., .05 or .01). These tables also provide information on the base rate, or frequency, of that difference in the normative sample.
WPPSI - Wechsler Preschool and Primary Scale of Intelligence Psychometric Properties and Norms Questions and Answers
An examiner notes that the WPPSI-IV Full Scale IQ (FSIQ) has an average internal consistency reliability coefficient of .95.
This value indicates which of the following about the FSIQ score?