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Essay on Test Evaluation
Psychological intelligence tests usually provide an estimate of global cognitive functioning as well as information about functioning within more specific domains. Compared to measures of virtually all other human traits, intelligence test scores are quite stable. However, the degree of stability increases with age such that early childhood and preschool measures of intellectual function are far less predictive of later functioning than assessments taken during middle childhood. Furthermore, despite their relative stability, intelligence test scores may change as a function of important environmental factors. Therefore, intelligence test scores are descriptive of a child's functioning at that point in time. This could change with alterations in the child's psychiatric status, environmental conditions, or educational program.
The Wechsler intelligence scales are the most popular among intelligence tests (Watkins et al., 1996; Wilson and Reschly, 1996), and therefore they will be described in greater detail than others. There are three different Wechsler intelligence tests that are structurally similar but differ with regard to the target age-range. The Wechsler Preschool and Primary Scale of Intelligence-Revised (WPPSI-R) (Wechsler, 1989) is the most recent version of the test normed for ages 3 to 7.3 years; the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) (Wechsler, 1991) is normed for ages 6 to 16 years, 11 months; and the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) (Wechsler, 1997) is normed for ages 16 through 74 years. All three are well-normed tests with considerable data supporting their reliability and validity.
The Wechsler tests generate three major IQ scores: Verbal IQ (VIQ), Performance IQ (PIQ), and Full Scale IQ (FSIQ). These are all deviation IQ scores standardized by age with a mean of 100 and SD of 15. Classification ranges are provided in the manuals such that the "average" range is considered to be between 90 and 109. "High average" is considered to be 110 to 119..................
