Evaluation of a Standardized Test Essay
Dr. David Wechsler was a clinical psychologist who, during his stint at the Bellevue Psychiatric Hospital, designed a number of tests that measured intelligence (Human, Intelligence, 2007). Date of publication: 1997 The WAIS-III is one of the three outcomes of several revisions of the Wechsler Bellevue Intelligence Scale, the other two being Wechsler Intelligence Scale for Children-III (WISC-III) and the Wechsler Preschool and Primary Scale of Intelligence-R (WPPSI-R).
The WAIS-III was first published in 1955, revised in 1981, and then revised anew in 1997 (Ford-Martin, 2002). The revision, which retained almost 80% of the of the original were done to check cultural bias (Wilderdom, 2004). Purpose of the test The WAIS – III is a comprehensive measurement of cognitive ability for adults and may be utilized for clinical, educational, and research purposes. Test results can also be used analyze the examinee’s personality and pathology (Ford-Martin, 2002). WAIS – III could also be used for neuropsychological assessment and diagnosis.
In the field of neuropsychology, disparities between verbal and non-verbal performance scores could also be used to evaluate the presence of brain dysfunction. Test results could also help determine “mental retardation, specific learning disabilities, and attention-deficit/hyperactivity disorder” (Ford-Martin, 2002). Population for which it was designed The WAIS – III is a general intelligence test for adults aged 16 – 89 years old. Construct being measured The WAIS – III measures intelligence as a global or multidimensional construct and not as a single intellectual functioning.
Wechsler characterized intelligence as the “… the global capacity of the individual to act purposefully, to think rationally, and to deal effectively with his environment. ” (Wechsler, 1981; as cited in Ford-Martin, 2002). Thus, the WAIS – III measures several intellectual competencies which include both verbal and non-verbal abilities. Norms One reason why the Wechsler scales was revised was to develop demographically adjusted norms gleaned from a contemporary standardized sample that considered geographical distribution and increased average life expectancy, among others.
The sample of 1,880 persons were randomly stratified into nine groups based on gender, ethnicity, geographical area, occupation, educational level, and urban-rural residence. Through the pioneering ideas of Wechsler, IQ scores gathered from the scales allow comparison of intelligence of the examinee with others in the same age range by converting the scores into percentile ranks. The distribution of WAIS – III scores shows nearly a normal curve which reflects average distribution of values and regular adjustments of the test are made to reflect a median score of 100 (Microsoft Encarta, 2007).
The Verbal, Performance, and Full Scale IQ scores are normative IQs, having a mean of 100 and a standard deviation of 15 while the 14 subtest scores have a mean of 10 and a standard deviation of three (Ford-Martin, 2002; Wilderdom. com). The index scores in the supplementary Index Scales have means of 100 and standard deviations of 15 (The IUPUI Counseling and Counselor Education Home Page). Later in this report, the geographically adjusted scores for neurodiagnostic analysis are presented.
So to preclude mistakes or confusion in interpreting the scores for neurodiagnosis and scores for intellectual assessment (general IQ scores), the former are reported on a “T-score metric with a mean of 50 and standard deviation of 10 scaled-score points” (Wilderdom. com, 2004). Internal structure of the test and test types: Scales and subscales The WAIS – III like other Wechsler scales has two batteries of subtests categorized as Verbal scales Performance scales with a total of 14 subtests or subscales.
The Verbal scales measure general knowledge, language, reasoning, and memory skills, while the Performance scales measure spatial, sequencing, and problem-solving skills (The IUPUI Counseling and Counselor Education Home Page). The WAIS-III contains the sub-scales with the competencies they measure described in the table below. For purposes of brevity, the number and nature and types of items are also presented although this topic will be explored more later in the succeeding section .