Scoring reliability on the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III)

Nineteen psychologists and 19 graduate students scored two Wechsler Adult Intelligence Scale-Third Edition patient protocols. Mean IQs and indexes were similar across groups, but the ranges for Verbal IQ (VIQ), Performance IQ (PIQ), and Full Scale IQ (FSIQ) on one protocol were 25, 22, and 11 points, respectively. For both protocols taken together, percentages of agreement with the "actual" IQs for psychologists were only 26.3 for VIQ, 36.8 for PIQ, and 42.1 for FSIQ. For students, percentages were 15.8 for VIQ, 23.7 for PIQ, and 31.6 for FSIQ. The percentages of FSIQs that fell within +/- 1 standard error of measurement of the actual IQs were 89.5 for psychologists and 76.3 for students. Scoring error also had a negative impact on index scores. Both groups were confident about their scoring accuracy.     

Orthogonal higher order structure and confirmatory factor analysis of the French Wechsler Adult Intelligence Scale (WAIS-III)

According to the most widely accepted Cattell-Horn-Carroll (CHC) model of intelligence measurement, each subtest score of the Wechsler Intelligence Scale for Adults (3rd ed.; WAIS-III) should reflect both 1st- and 2nd-order factors (i.e., 4 or 5 broad abilities and 1 general factor). To disentangle the contribution of each factor, we applied a Schmid-Leiman orthogonalization transformation (SLT) to the standardization data published in the French technical manual for the WAIS-III. Results showed that the general factor accounted for 63% of the common variance and that the specific contributions of the 1st-order factors were weak (4.7%-15.9%). We also addressed this issue by using confirmatory factor analysis. Results indicated that the bifactor model (with 1st-order group and general factors) better fit the data than did the traditional higher order structure. Models based on the CHC framework were also tested. Results indicated that a higher order CHC model showed a better fit than did the classical 4-factor model; however, the WAIS bifactor structure was the most adequate. We recommend that users do not discount the Full Scale IQ when interpreting the index scores of the WAIS-III because the general factor accounts for the bulk of the common variance in the French WAIS-III. The 4 index scores cannot be considered to reflect only broad ability because they include a strong contribution of the general factor.     

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.     

Replication of the factor structure of the Wechsler Adult Intelligence Scale--Third Edition with a Canadian sample

Exploratory and confirmatory factor analyses of the subtests of the Wechsler Adult Intelligence Scale--Third Edition (WAIS-III; D. Wechsler, 1997b) were conducted on a stratified sample of Canadian adults (n = 718). As was previously demonstrated for the children's version of this scale, the factor model of the American standardization sample was replicated across this Canadian national sample. Results of the factor analyses confirmed the presence of the 4 WAIS-III factors: Verbal Comprehension, Perceptual Organization, Working Memory, and Processing Speed.     

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.     

Education-stratified base-rate information on discrepancy scores within and between the Wechsler Adult Intelligence Scale--Third Edition and the Wechsler Memory Scale--Third Edition

The Wechsler Adult Intelligence Scale--Third Edition (WAIS-III; D. Wechsler, 1997a) and the Wechsler Memory Scale--Third Edition (WMS-III; D. Wechsler, 1997b) are 2 of the most frequently used measures in psychology and neuropsychology. To facilitate the diagnostic use of these measures in the clinical decision-making process, this article provides information on education-stratified, directional prevalence rates (i.e., base rates) of discrepancy scores between the major index scores for the WAIS-III, the WMS-III, and between the WAIS-III and WMS-III. To illustrate how such base-rate data can be clinically used, this article reviews the relative risk (i.e., odds ratio) of empirically defined "rare" cognitive deficits in 2 of the clinical samples presented in the WAIS-III--WMS-III Technical Manual (The Psychological Corporation, 1997).     

Factor structure of the Wechsler Adult Intelligence Scale-III in schizophrenia

This report examines and compares the factor structure of the new edition of the Wechsler Adult Intelligence Scale (WAIS-III) in a sample of chronic schizophrenia and schizoaffective disorder outpatients (n = 120) and an age-matched sample of individuals drawn from the WAIS-III standardization sample (n = 200). Exploratory and confirmatory factor analyses similar to those reported by the developers of the scale suggested that a model of WAIS-III performance with correlated factors for verbal comprehension, perceptual organization, working memory, and processing speed fit the data from the schizophrenia sample as well as it fit the nonclinical comparison sample and fit the data from both samples better than alternative models.     

Factorial invariance in multilevel confirmatory factor analysis

This paper presents a procedure to test factorial invariance in multilevel confirmatory factor analysis. When the group membership is at level 2, multilevel factorial invariance can be tested by a simple extension of the standard procedure. However level‐1 group membership raises problems which cannot be appropriately handled by the standard procedure, because the dependency between members of different level‐1 groups is not appropriately taken into account. The procedure presented in this article provides a solution to this problem. This paper also shows Muthén's maximum likelihood (MUML) estimation for testing multilevel factorial invariance across level‐1 groups as a viable alternative to maximum likelihood estimation. Testing multilevel factorial invariance across level‐2 groups and testing multilevel factorial invariance across level‐1 groups are illustrated using empirical examples. SAS macro and Mplus syntax are provided.     

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.     

A confirmatory factor analysis of the structure of schizotypy

Recent research into schizotypal traits has been concerned with the number and nature of these personality dimensions. Earlier exploratory factor analytic work using a wide variety of scales (the CSTQ) has generated a four-factor solution but other solutions have been provided by other investigators. This study uses confirmatory factor analysis on a large sample to compare several plausible models of the relationships between scales. These models include a two-factor model separating ‘positive’ from ‘negative’ schizotypal features, a three-factor model including features of cognitive disorganization, and the four-factor model generated previously by exploratory factor analysis. Results offer support for the four-factor solution as the only structure meeting multiple criteria for goodness of fit. The relevance of Eysenck's dimensions, and the P scale in particular, to the results is discussed. Attention is drawn to the possibility that the factors describe predispositions of risk of psychotic disorders beyond that of schizophrenia.     

Factor analysis of Wechsler Adult Intelligence Scale-Revised in developmentally disabled persons

The results of previous studies on the factorial structure of Wechsler Intelligence Scales are somewhat inconsistent across normal and pathological samples. To study specific clinical groups, such as developmentally disabled persons, it is useful to examine the factor structure in appropriate samples. A factor analysis was carried out using the principal component method and the Varimax orthogonal rotation on the Wechsler Adult Intelligence Scale (WAIS-R) in a sample of 203 developmentally disabled persons, with a mean age of 25 years 4 months. Developmental disability ranged from mild to moderate. Partially contrasting with previous studies on normal samples, results found a two-factor solution. Wechsler's traditional Verbal and Performance scales seems to be more appropriate for this sample than the alternative three-factor solution.     

Dyadic short forms of the Wechsler Adult Intelligence Scale-III

Various short forms of the Wechsler Adult Intelligence Scale (WAIS)/WAIS-R have been developed to obtain estimates of overall intellectual level, although little research of WAIS-III short forms has been published to date. Full Scale IQ (FSIQ) estimatesfromfour WAIS-III dyadic short forms were obtained by entering selected subtest scores from a mixed neurologic/ psychiatric sample (n = 196) into regression equations. Results were cross validated on a second sample (n = 57). Within both samples, WAIS-III FSIQ scores were highly correlated (r = .90-.92, p < .001) with estimated FSIQ scores. Estimated FSIQ fell within 5 points of actual FSIQ in 49% to 74% of cross-validation cases and within 10 points of actual FSIQ in 81% to 93% of the sample. Comparable to findings from previous short-form investigations, actual and estimated FSIQ classification levels agreed in 46% to 67% of cases in the cross-validation sample. These dyadic WAIS-III forms appear appropriate for obtaining gross estimates of FSIQ in similar populations, although caution is recommended in interpreting estimated IQ scores.     

Alternative factor models and factorial invariance of the GHQ-12: a large sample analysis using confirmatory factor analysis

This study tested alternative factor models of the General Health Questionnaire-12 (GHQ-12), based on previous research findings, with a large sample using confirmatory factor analysis. An alternative models framework was used to test 6 factor analytic models. A 3-factor model was the best explanation of the sample data. The 3 factors were labeled Anxiety-Depression, Social Dysfunction, and Loss of Confidence. The model was found to be factorially invariant between men and women. The utility of the 3 subscales, as opposed to the total GHQ-12 score, is questioned as they appear to provide little information beyond that of a general factor.     

Increasing the reliability of Wechsler Intelligence Scale for Children--Third Edition difference scores with reliable component analysis

Wechsler Intelligence Scale for Children--Third Edition index score differences are generally interpreted cautiously, if at all, primarily because of their poor reliability. On the basis of prior analyses with the Wechsler Adult Intelligence Scale--Third Edition (J. C. Caruso & N. Cliff, 1999), it was hypothesized that differences between scores defined by reliable component analysis would have higher reliability than those defined by traditional equal weighting. Differences between the reliable component scores showed substantially higher reliability than equally weighted score differences. The differences between reliable component scores were also substantially more reliable than those derived from the weighted scores suggested by K. C. H. Parker and L. Atkinson (1994). Using the weights provided in this article will allow researchers and practitioners to compute the RCA scores and have the assurance of high reliability with its attractive consequences.     

Sex differences in the structure of intelligence: A confirmatory factor analysis

The LISREL model of Jöreskog and Sörbom was used to perform a comparative factor analysis on intelligence data from four sex by generation groups. The covariance matrices for 10 psychometric ability measures were used to isolate Spatial and Verbal Intelligence factors. Results from a series of factor analysis models indicated substantial invariance in the factor pattern and factor covariance matrices, although the hypothesis of complete invariance in factor pattern was rejected. The groups did differ in observed and unique variances. The results were basically consistent with the hypothesis that males and females have similar intellectual structure, which would have been obscured had standardized factor analysis been employed. There were also sex and generation differences in the Spatial and Verbal factor means.     

A longitudinal study of the performance of hypertensive and normotensive subjects on the Wechsler Adult Intelligence Scale

Performance on the Wechsler Adult Intelligence Scale was followed over two 5- to 6-year intervals for essential hypertensive Ss (EH; n = 22) free from medical complications and for normotensive Ss (N; n = 20). EH were treated with adrenergic beta-blocking drugs, diuretics, or both. Mean age was 46 years (SD = 12.6 years), initially (Time 1). Results were unaltered by adjustment for initial age. N improved modestly on the Verbal scale, from Time 1 to Time 2 only. EH neither improved nor declined on the Verbal scale. Scores remained unchanged for both EH and N Ss for the Performance scale. Overall, and at Times 2 and 3, Verbal scores were lower for the EH group. It was concluded that neither decline nor improvement in cognitive function over time are necessary outcomes of modest, carefully treated, uncomplicated hypertension in the middle years.     

A confirmatory analysis of the factor stability hypothesis

The procedures recently developed by Jöreskog for studying similarities and differences in factor structures between different groups were applied to data from a study designed by Thurstone to investigate the sampling stability of a hypothesized isolated configuration. The hypothesis of an isolated configuration was rejected but not by much. The results represent a restricted and unique simple structure solution with the factor loadings and uniqueness values invariant over the two samples.     

A confirmatory factor analysis of the California Verbal Learning Test--Second Edition (CVLT-II) in the standardization sample

The purpose of this study is to determine the latent structure of the California Verbal Learning Test-Second Edition (CVLT-II; Delis, Kramer, Kaplan, & Ober, 2000) at three different age levels, using the standardization sample. Maximum likelihood confirmatory factor analyses are performed to test four competing hypothetical models for fit and parsimony. A four-factor model consisting of Attention Span, Learning Efficiency, Delayed Memory, and Inaccurate Memory provides the best fit to the data at two age levels (16-30 years and 31-60 years, respectively) but the factor structure is somewhat less robust in the oldest age group (>60 years). The results clarify the latent structure of the CVLT-II and suggest that a multifactorial interpretation of quantitative and qualitative indexes from this instrument is appropriate for clinical practice with most adults, although findings may need to be interpreted more cautiously among older persons.     

A bayesian approach to confirmatory factor analysis

Confirmatory factor analysis is considered from a Bayesian viewpoint, in which prior information on parameter is incorporated in the analysis. An iterative algorithm is developed to obtain the Bayes estimates. A numerical example based on longitudinal data is presented. A simulation study is designed to compare the Bayesian approach with the maximum likelihood method.Computer facilities were provided by the Computer Services Center, The Chinese University of Hong Kong.