A Confirmatory Analysis of the Factor Structure and Cross-Age Invariance of the Wechsler Adult Intelligence Scale-Third Edition.

In the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; D. Wechsler, 1997), the manual reports several confirmatory factor analyses in support of the instrument's latent factor structure. In practice, examiners frequently compare an examinee's score from a current administration of the WAIS-III with the results from a previous test administration. Implicit in test-retest score comparisons is evidence that scores retain similar interpretive meaning across time. Establishing an instrument's factorial invariance provides the foundation for this practice. This study investigated the factorial invariance of the WAIS-III across the instrument's 13 age groups. The overall results from this study generally support both configural and factorial invariance of the WAIS-III when the 11 primary tests are administered. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Ipsative Comparisons of Index Scores for the Canadian WAIS-III.

The Canadian standardization of the Wechsler Adult Intelligence Scale--Third Edition (WAIS-III; Wechsler, 1997a, 2001) provides factor-based index scores, giving an intermediate level of analysis between IQ scores and individual subtests. This article provides tables for comparing all indices to the mean index score, and for identifying the statistical significance and relative frequency of obtained differences. This simultaneous or ipsative approach can avoid some of the statistical and logical pitfalls of multiple pairwise comparisons, such as decreased interpretability and inflated risk of Type I errors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

General Ability Index for the WAIS-III: Canadian Norms.

The Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; Wechsler, 1997) permits the calculation of both traditional IQ and Index scores. The Verbal Comprehension and Perceptual Organization indexes are the most highly "g" loaded compared to the Working Memory and Processing Speed indexes that may be more sensitive to some neuro-cognitive disorders. In certain clinical situations, a general ability composite score based on the combination of only the verbal and performance indexes is desirable. Following the procedure for calculating a General Ability Index (GAI; Prifitera, Weiss, & Saklofske, 1998) for the Wechsler Intelligence Scale for Children-Third Edition (WISC-HI; Wechsler, 1991) and the WAIS-III (Tulsky, Saklofske, Wilkins, & Weiss, 2001), GAI normative tables for the WAIS-III Canadian standardization sample are reported here to complement earlier published GAI Canadian norms tables for the WISC-III. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The joint WAIS-III and WMS-III factor structure: Development and cross-validation of a six-factor model of cognitive functioning.

During the standardization of the Wechsler Adult Intelligence Scale (3rd ed.; WAIS-III) and the Wechsler Memory Scale (3rd ed.; WMS-III) the participants in the normative study completed both scales. This "co-norming" methodology set the stage for full integration of the 2 tests and the development of an expanded structure of cognitive functioning. Until now, however, the WAIS-III and WMS-III had not been examined together in a factor analytic study. This article presents a series of confirmatory factor analyses to determine the joint WAIS-III and WMS-III factor structure. Using a structural equation modeling approach, a 6-factor model that included verbal, perceptual, processing speed, working memory, auditory memory, and visual memory constructs provided the best model fit to the data. Allowing select subtests to load simultaneously on 2 factors improved model fit and indicated that some subtests are multifaceted. The results were then replicated in a large cross-validation sample (N=858). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of demographic norms for four new WAIS-III/WMS-III indexes.

Following the publication of the third edition Wechsler scales (i.e., WAIS-III and WMS-III), demographically corrected norms were made available in the form of a computerized scoring program (i.e., WAIS-III/WMS-III/WIAT-II Scoring Assistant). These norms correct for age, gender, ethnicity, and education. Since then, four new indexes have been developed: the WAIS-III General Ability Index, the WMS-III Delayed Memory Index, and the two alternate Immediate and Delayed Memory Indexes. The purpose of this study was to develop demographically corrected norms for the four new indexes using the standardization sample and education oversample from the WAIS-III and WMS-III. These norms were developed using the same methodology as the demographically corrected norms made available in the WAIS-III/WMS-III/WIAT-II Scoring Assistant. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Age-related invariance of abilities measured with the Wechsler Adult Intelligence Scale-III.

Examination of measurement invariance tests the assumption that the model underlying a set of test scores is directly comparable across groups. The observation of measurement invariance provides fundamental evidence for the inference that scores on a test afford equivalent measurement of the same psychological traits among diverse groups. Groups may be derived from different psychosocial backgrounds or different clinical presentations. In the Wechsler Adult Intelligence Scale-III (WAIS-III)/Wechsler Memory Scale-III (WMS-III) Technical Manual (Psychological Corporation, 2002), there appears to be a breakdown in factor structure among the standardization cases in older adults. In this study, the authors evaluated the invariance of the measurement model of the WAIS-III across 5 age bands. All components of the measurement model were examined. Overall, the evidence pointed to invariance across age of a modified 4-factor model that included cross-loadings for the Similarities and Arithmetic subtests. These results support the utility of the WAIS-III as a measure of stable intelligence traits across a wide age range. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of a General Ability Index for the Wechsler Adult Intelligence Scale—Third Edition.

The Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; D. Wechsler, 1997) permits the calculation of both traditional IQ and index scores. However, if only the subtests constituting the index scores are administered, especially those yielding the Verbal Comprehension and Perceptual Organization Indexes, there is no equivalent measure of Full Scale IQ. Following the procedure for calculating a General Ability Index (GAI; A. Prifitera, L. G. Weiss, & D. H. Saklofske, 1998) for the Wechsler Intelligence Scale for Children - IIIrd Edition (WISC--III) (D. Wechsler, 1991), GAI normative tables for the WAIS-III standardization sample are reported here. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Canadian WISC-III directional base rates of score discrepancies by ability level.

A recent advancement in the clinical interpretation of test scores from the Wechsler Intelligence Scale for Children-Third Edition (WISC-III; Wechsler, 1991) and the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; Wechsler, 1997) is the use of antecedent probability or base rate data. However, the WISC-III only included a single table that did not reflect the direction of score differences. The Canadian standardization data for the WISC-III (The Psychological Corporation, 1996) were employed to create two-directional base rate tables based on five ability levels. These more comprehensive tables are in line with the approach frequently taken by psychologists in the interpretation of intelligence test data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Values for Comparison of WAIS-III Index Scores With Overall Means.

The Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; Wechsler, 1997b) provides factor-based index scores but allows only for pairwise comparison of these scores, producing inflated Type I error rates and reducing profile interpretability. This article provides tables for simultaneous comparison to the overall mean index score, thus reducing error rates and aiding interpretation. The Working Memory Index or Processing Speed Index can also be specifically compared when an individual is believed to have a condition, such as a learning disability or traumatic brain injury, associated with the selective depression of these indexes. Tables for the infrequency of specific differences are also provided, allowing the practitioner to note how unusual an obtained difference is in the general population. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Supplementary WMS-III tables for determining primary subtest strengths and weaknesses.

It is common practice to evaluate the age-adjusted subtest scores from the Wechsler intelligence scales to determine strengths and weaknesses within a profile. The Wechsler Memory Scale-III (WMS-III; D. Wechsler, 1997a) represents a significant improvement over its predecessors and, for the first time, provides age-adjusted subtest scores for interpretation, just as the Wechsler intelligence scales have done for 60 years. It is reasonable to assume that examiners will evaluate the WMS-III subtest profiles for strengths and weaknesses. However, the WMS-III Administration and Scoring Manual and the WAIS-III—WMS-III Technical Manual (The Psychological Corporation, 1997) provide no assistance for accomplishing this goal. Data from the WMS-III standardization sample, as described in the WAIS-III-WMS-III Technical Manual, were used to develop tables for determining both confidence levels and infrequency of differences between individual subtest scores and the means of 5 subtest combinations that may be clinically relevant for individual cases. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Wechsler Adult Intelligence Scale-Third Edition short form for index and IQ scores in a psychiatric population.

An eight-subtest short form (SF8) of the Wechsler Adult Intelligence Scale, Third Edition (WAIS-III), maintaining equal representation of each index factor, was developed for use with psychiatric populations. Data were collected from a mixed inpatient/outpatient sample (99 men and 101 women) referred for neuropsychological assessment. Psychometric analyses revealed an optimal SF8 comprising Vocabulary, Similarities, Arithmetic, Digit Span, Picture Completion, Matrix Reasoning, Digit Symbol Coding, and Symbol Search, scored by linear scaling. Expanding on previous short forms, the current SF8 maximizes the breadth of information and reduces administration time while maintaining the original WAIS-III factor structure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Developments in neuropsychological assessment: Refining psychometric and clinical interpretive methods.

The goal of this article is to discuss psychometric issues that are important in neuropsychological assessment and to present some recent advances in empirically derived interpretation methods. The article is divided into four main sections. The first two sections provide an overview of some of the basic psychometric concepts that make up the foundation of assessment. The first section presents an overview of how the adequacy of the normative sample and the shape of the score distribution can impact the interpretation of test performance. The second section presents a review of the role of measurement error and considers how the level of scores, their rank in the distribution, and the presence of ceiling or floor effects can impact interpretation. The third section explores the issue of normal variability and the prevalence of “abnormal” test scores in healthy people. The final section provides an overview of various methods for interpreting change in test performance over time. The authors present this psychometric information in a manner that should be easily understood by most clinicians, with examples that employ commonly used neuropsychological tests, such as the Wechsler Adult Intelligence Scale–Third Edition (WAIS-III; Wechsler, 1997a), Wechsler Adult Intelligence Scale–Fourth Edition (WAIS-IV; Wechsler, 2008), Wechsler Memory Scale–Third Edition (WMS-III; Wechsler, 1997b), Wechsler Memory Scale–Fourth Edition (WMS-IV; Wechsler, 2009), Children’s Memory Scale (CMS; Cohen, 1997), California Verbal Learning Test–Second Edition (CVLT-II; Delis, Kramer, Kaplan, & Ober, 2000), and the Neuropsychological Assessment Battery (NAB; Stern & White, 2003). (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Seeing the forest for the trees: Prevalence of low scores on the Wechsler Intelligence Scale for Children, fourth edition (WISC-IV).

Low scores across a battery of tests are common in healthy people and vary by demographic characteristics. The purpose of the present article was to present the base rates of low scores for the Wechsler Intelligence Scale for Children, fourth edition (WISC-IV; D. Wechsler, 2003). Participants included 2,200 children and adolescents between 6 and 16 years of age from the WISC-IV U.S. standardization sample. Measures considered in the base rates analyses included the 10 core subtests and the 4 index scores. Analyses were conducted for the entire standardization sample as well as stratified by different classifications of intelligence and different years of parental education. In the total sample, it is uncommon to have 6 or more subtest scores or 2 or more Index scores ≤ 9th percentile. The prevalence of low scores typically increased with lesser intelligence and fewer years of parental education (e.g., children with below-average intelligence were 75 times more likely than children with above-intelligence to have at least one impaired subtest score). Consistent with existing studies of the base rates of low scores, some low scores on the WISC-IV were common in children and adolescents, and the frequency was related to a child's level of intelligence and parental education. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Confirmatory factor analysis of the WMS-III in patients with temporal lobe epilepsy.

Five competing models specifying the factor structure underlying the Wechsler Memory Scale--Third Edition (D. Wechsler, 1997b) primary subtest scores were evaluated in a sample of patients with intractable temporal lobe epilepsy (N=254). Models specifying separate immediate and delayed constructs resulted in inadmissible parameter estimates and model specification error. There were negligible goodness-of-fit differences between a 3-factor model of working memory, auditory memory, and visual memory and a nested--more parsimonious--2-factor model of working memory and general memory. The results suggest that specifying a separate visual memory factor provides little advantage for this sample--an unexpected finding in a population with lateralized dysfunction, for which one might have predicted separate auditory and visual memory dimensions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Confirmatory factor analysis of the Wechsler Intelligence Scale for Children-Third Edition in an Australian clinical sample.

A confirmatory factor analysis was conducted on the Wechsler Intelligence Scale for Children-Third Edition (WISC-III; D. Wechsler, 1991) with a sample of 579 Australian children referred for assessment because of academic difficulties in the classroom. The children were administered the WISC-III as part of the initial eligibility determination process for funding of special education services. The children were aged between 6 years and 16 years 7 months. One-, two-, three-, and four-factor models were tested. The four-factor model proposed in the WISC-III manual fit the data significantly better than all other models tested. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two-subtest estimations of WAIS-III factor index scores.

The reliability and validity of various short forms of the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; D. Wechsler, 1997) were evaluated in a sample of 100 patients with traumatic brain injury and in a demographically matched subgroup from the standardization sample. All short forms were based on 2-subtest estimations of the respective factor indexes. Although acceptable estimates could be obtained from all short forms for Verbal Comprehension, none of the possible short forms for Perceptual Organization consistently met the minimum criterion regarding the percentage of cases that fell within the 90% confidence interval of the full-length index. It is concluded that short-form estimates of the WAIS-III are not appropriate for clinical use when the goal is to obtain factor indexes. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Two abbreviated versions of the Wechsler Adult Intelligence Scale-III: Validation among persons with traumatic brain injury.

Objective: To examine the clinical value of two 7-subtest versions of the Wechsler Adult Intelligence Scale-III (WAIS-111): one using Block Design (WAIS-III/BD7) and another using Matrix Reasoning (WAIS-III/MR7) among persons with traumatic brain injury (TBI). Study Design: Actual obtained scores from the full WAIS-111 were compared with scores that would have been obtained using each of the two abbreviated versions. Participants: One hundred eighteen persons with TBI tested consecutively in an academic medical center outpatient neuropsychology laboratory. Results: For the WAIS-IIVBD7, corrected validity coefficients were .97 (Verbal IQ [VIQI), .94 (Performance IQ [PIQ]), and .97 (Full Scale IQ [FSIQJ); 92%, 70%, and 92% of scores fell within 5 points of full version scores for VIQ, PIQ, and FSIQ, respectively. WAIS-III/MR7 corrected validity coefficients were .97 (VIQ), .95 (PIQ), and .97 (FSIQ); 92%, 76%, and 92% of short-form scores were within 5 points of actual scores for VIQ, PIQ, and FSIQ, respectively. Conclusions: Both abbreviated versions demonstrated acceptable psychometric characteristics, but the matrix reasoning version may be more advantageous in assessing persons with TBI because it can be used with persons who have TBI-related motor skills impairment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estimating the percentage of the population with abnormally low scores (or abnormally large score differences) on standardized neuropsychological test batteries: A generic method with applications.

Information on the rarity or abnormality of an individual's test scores (or test score differences) is fundamental in interpreting the results of a neuropsychological assessment. If a standardized battery of tests is administered, the question arises as to what percentage of the healthy population would be expected to exhibit one or more abnormally low test scores (and, in general, j or more abnormally low scores). Similar issues arise when the concern is with the number of abnormal pairwise differences between an individual's scores on the battery, or when an individual's scores on each component of the battery are compared with the individual's mean score. A generic Monte Carlo simulation method for tackling such problems is described (it requires only that the matrix of correlations between tests be available) and is contrasted with the use of binomial probabilities. The method is then applied to Index scores for the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III; D. Wechsler, 1997) and Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV; D. Wechsler, 2003). Three computer programs that implement the methods are made available. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prediction of unilateral brain dysfunction using Wechsler test scores.

This study investigated whether oblique factor scores for Wechsler tests discriminate right- and left-hemisphere brain dysfunction more effectively than subtest or scale scores. A criterion sample of 60 psychomotor-seizure epileptics was divided into 2 equal cross- validation groups with comparable proportions of right and left Ss. 3 measures of lateralization were used, with a criterion cut-off of at least 2 measures lateralizing each S. A computer-programmed, "stepwise" regression analysis was performed utilizing a double cross-validation design. Regular scale scores proved more effective than factor scores, although the latter were nearly comparable using a different factor-extraction matrix. (22 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

David Wechsler (1896-1981).

Memorializes David Wechsler, who helped to provide clinical psychology with a tool (his scales) and with a humanistic philosophy toward the use of such tools (i.e., that assessment is not synonymous with testing). As a result, clinical psychologists working on a one-on-one basis in a variety of settings have provided a professional service which has been voluntarily sought out and appreciated by clients and patients throughout the world. Beginning in 1934, Wechsler's creative efforts were largely directed to two of his most important contributions to psychology: (a) the development and standardization of the adult (and later preschool and children's) intelligence scales that bear his name; and (b) the substitution for Binet's Mental Age of a Deviation Quotient (so important in evaluating the intelligence level of adults) that related each person's raw intelligence test score to his or her own age group as a reference, rather than to a mental age and an upper age limit of 15 years for adults, as had been done by Binet, Terman, and others. (PsycINFO Database Record (c) 2010 APA, all rights reserved)