Presentation on theme: "Overview of Wechsler Scales David Wechsler originally introduced Wechsler-Bellevue Intelligence Scale in 1939, an intellectual test for adults. Revised."— Presentation transcript:
Overview of Wechsler Scales David Wechsler originally introduced Wechsler-Bellevue Intelligence Scale in 1939, an intellectual test for adults. Revised version (WAIS) introduced in 1955, 1981 and most recent WAIS-III (1997) WAIS-III (16-89 years of age).
Wechsler Overview (continued) Wechsler Preschool and Primary Scale of Intelligence (age range = 3 years to 7 years, 3 months). Wechsler Intelligence Scale for Children (1949) was introduced as a downward extension of the Wechsler-Belleuve Adult Intelligence Scale. WISC-III appeared in 1991 and WISC-IV appeared in summer of Children from 6 to 16 years, 11 months.
Overview of WISC-III Standardization - N= 2, boys and girls from each year from 6.5 to Stratified random sample using 1988 U.S. Census (variables = region, urban vs. rural, occupation and race). Reliability- Good internal consistency. Average K-R =.96 (FS),.95(V), and.91(P). Also, good test-retest reliability. Mean test-retest increase 7(FS), 2(V), and 12.5(P).
Overview of WISC-III (continued) Validity - Good concurrent validity with the Stanford-Binet (.80). Factor Analytic Results 2 factors (Verbal and Perceptual- Organizational) emerged across all ages. WPPSI-R - 2 Factor Solution. WISC-III - 4 factor model including VC, PO, FD, and Processing Speed. For WAIS-R - 3 factor solution consisting of VC, PO, and Memory/Freedom from Distractibility.
Overview of WISC-IV Standardization - N= 2, boys and girls from each year from 6.5 to Stratified random sample using 2000 U.S. Census (variables = region, urban vs. rural, occupation and race). Reliability- Good internal consistency. K-R =.97(FS),.91 to.95(Verbal Comprehension),.91 to.93 (Perceptual Reasoning), Working Memory (.90 to.93), & Processing Speed (.81 to.9).
Overview of WISC-IV (continued) Also, good test-retest reliability. 5 age groups (13-63 days). Average test-retest reliability (.93). Mean test-retest increase 6 (FS), 2 (VC), 5 (Perceptual Reasoning), 3 (Working Memory), 7 (processing speed).
Overview of WISC-IV (continued) Correlation with other measures Full Scale IQ WISC-III (.89) WPPSI-III (.89) WAIS-III (.89)
Administration All subtests may be given to children of all ages minutes in length. Many of the subtests start with the first item for all children; others begin at different points based on a child’s age. No routing subtest(s). For those subtests which begin at different places based on age, if the child correctly answers the first two items, they are given credit for all items before those two.
Administration (continued) If the child misses either of these items, they are administered preceding items in reverse order until the child passes two items. The Ceiling was each subtest was set individually (e.g., 2 items for Block Design; 4 for Vocabulary).