You’ll recall the development of adult lessons on mathematics for children with mental retardation tests from earlier in the semester I hope. Thus, the WISC III offered a FSIQ as a measure of g, a Verbal and a Performance IQ for those used to the WISC R, and four new factors.
These were the Verbal Comprehension Index, Perceptual Organization Index, Freedom from Distractibility Index, and Processing Speed Index. Of note, while the Psychological Corporation believed the factor structure supported these four factors, Sattler had some doubts. The WISC IV is an update of the WISC III, and contains 10 core subtests, and 5 additional subtests, that can be summed to four indexes, and one Full Scale IQ. The FSIQ can range from 40 at the lowest to 160 at the highest. Three subtests can be given in modified forms to allow for additional examination of processing abilities. The test takes between 65 and 80 minutes to administer to most children, with more time required if the additional subtests are given or if the client is more intelligence, and less time required for clients suffering from Mental Retardation.
It can be given to children as young as 6,0 and as old as 16,11. The test overlaps with the Wechsler Preschool and Primary Scale of Intelligence — Third Edition for children between the ages of 6,0 and 7,3. While research has not been collected to determine the effect of practice on re-examination, research based on the WISC III indicated that one year was needed between administrations to avoid significant practice effects. Over the WISC IV test-retest period of 32 days, the VCI gained 2-3 points, PRI gained 3-6 points, WMI gained 1-5 points, and PSI gained 5-11 points.