0 1990 Gordon
J . Neuroscience, 1990, Vol. 55, pp. 107-1 I 1 Reprints available directly from the publisher Photocopying permitted by license only Intern.
and Breach Science Publishers S.A. Printed in the United Kingdom
Brief Communication FACTOR ANALYSIS OF THE MAINLAND CHINESE VERSION OF THE WECHSLER ADULT INTELLIGENCE SCALE (WAIS-RC) IN A BRAINDAMAGED SAMPLE XIAOYANG DAT
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
Psychological Research Unit, Hunan Medical University, Changsha, People’s Republic of China
JOSEPH J. RYAN and ANTHONY M. PAOLO Dwight D . Eisenhower Department of Veterans Aflairs Medical Center Leavenworth, Kansas, USA
ROBERT G. HARRINGTON University of’ Kansas, Lawrence, Kansas, USA (Received May 17, 1990) We factor analyzed the Chinese revision of the Wechsler Adult Intelligence Scale (WAIS-RC) in a sample of 59 individuals with medically diagnosed brain damage. The Chinese subjects consisted of 42 males and 17 females with means for Verbal, Performance, and Full Scale IQ of 83.88 (SD = 22.11), 75.49 (SD = 20.63), and 78.42 ( S D = 21.97), respectively. Clear support was found for a general intelligence factor (g) and the Full Scale IQ. Similarly, the two-factor solution provided support for Wechsler’s (1981) Verbal and Performance IQ designations. The three-factor solution revealed the familiar VerbalComprehension and Perceptual-Organization factors. However, the Freedom From Distractibility factor was less clearly defined. Comparisons of Chinese and American factor structures for neurologically impaired persons demonstrated high coefficients of congruence, ranging from .93 to .98. Overall, the findings demonstrated substantial congruence cross culturally for Chinese and American brain-damaged samples and suggest that the WAIS-RC measures essentially the same constructs a s the WAIS-R. Keywords: Brain damage. WAIS-RC, Factor analysis
The Wechsler Adult Intelligence Scale (WAIS; Wechsler, 1955) has been translated, modified, and standardized for application within the People’s Republic of China. The new test, which is known as the Wechsler Adult Intelligence Scale-Revised for China (WAIS-RC; Gong, 1982), has been widely used in medical and educational settings. The WAIS-RC consists of 1 1 subtests and maintains Wechsler’s logic-based Verbal-Performance dichotomy. Factor analytic studies of the Chinese standardization sample (Dai, Gong, & Zhong, 1990) indicate that the WAIS-RC factor structure and variance components are highly similar to those of the American WATS and Wechsler Adult Intelligence Scale-Revised (WAIS-R; Wechsler, 1981). These findings
Requests for reprints should be sent to Joseph J. Ryan, Chief, Psychology Service (1 16B). DDE DVA Medical Center, Leavenworth, KS66048.
107
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I08
trl
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
suggest that factor-based clinical interpretations previously established for the WAIS and WAIS-R (Matarazzo, 1972; Parker, 1983) may generalize to the WAIS-RC. Dai et al. (1990) reported that the WAIS-RC is frequently used in the assessment of persons with suspected or confirmed brain disorders. However, there are no published studies which elucidate the factor structure of the scale within a neurologically comprised sample. The present investigation was intended to rectify this situation by reporting the results of a principal-factor analysis of the WAIS-RC in a diagnostically heterogeneous group of brain-impaired individuals. The second purpose of the study was cross-cultural and compared the WAIS-RC structure with that of an American sample of brain-damaged patients tested with the WAIS-R (Ryan & Schneider, 1986). METHOD Subjec t.7
The sample consisted of 59 neurology inpatients from three medical school affiliated hospitals located in the southwestern region of the People’s Republic of China. For each subject, brain-damage was diagnosed by a team of physicians based on the results of a medical history, neurological examination, and at least one of the following: Computed axial tomography scan, angiogram, or neurosurgical report. Seven patients had left hemisphere damage, seven had right hemisphere lesions, and 45 were considered to have bilateral brain damage. Table 1 provides demographic information on the sample in terms of age, sex distribution, and education. Means and standard deviations on the WAIS-RC subtests and IQs appear in Table 2.
TABLE 1 Demographic Characteristics of the Chinese Brain-Damaged Sample Variable
n
%
Sex Male Fcmalc
42
11.2 28.8
17
Age
1.7 3.4 15.3 10.2 20.3 16.9 23.1
> 65
1 2 9 6 12 10 14 5
Education 0- 3 4- 8 9 II 12-14 > 15
5 19 20 6 9
8.5 32.2 33.9 10.2 15.3
16-17 18-19 20-24 25-34 35-44 45-54 55-64
8.5
WAIS-RC FACTOR ANALYSIS
109
TABLE 2 Means and Standard Deviations for WAIS-RC 1Qs and Subtest Scores
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Variables Information Digit Span Vocabulary Arithmetic Comprehension Similarities Picture Completion Picture Arrangement Block Design Object Assembly Digit Symbol Verbal IQ Performance IQ Full Scale IQ
Mean
SD
8.00 7.86 7.51 6.66 8.20 6.59 5.63 5.61 6.36 6.19 6.00
3.91 3.55 3.52 4.22 4.0 1 3.64 3.04 3.83 3.20 3.44 3.23
83.88 75.49 78.42
22.11 20.63 21.97
Procedure
Each examination was conducted by a member of the National Psychological Testing Coworker Group of China from 1981 to 1985. All 11 subtests of the WAIS-RC were administered to each patient by a trained examiner according to standardized instructions (Gong, 1982). Intercorrelations of scaled scores on the WAIS-RC subtests were obtained and subjected to a principal-factor analysis with iterations (squared multiple correlations in the diagonal) followed by varimax rotation of two- and three-factors. The degree of similarity between orthogonal factors for the WAIS-RC and those from the Ryan and Schneider (1986) study was assessed with the coefficient of congruence. Since Ryan and Schneider reported only a three-factor solution in their original paper, it was necessary to reanalyze their data so that a two-factor solution was also available for comparison with the Chinese sample. RESULTS AND DISCUSSION Following Gutkin, Reynolds, and Galvin (1984), subtest loadings on the first unrotated factor of the two-factor solution were taken as measures of each subtest’s relationship with general intelligence (8). For the Chinese subjects, there was clear support for a robust g factor and the validity of the Full Scale IQ. Every subtest displayed a sizable loading on the first unrotated factor with values ranging from a low of .53 on the Digit Span to a high of .80 on Block Design and Picture Arrangement. The unrotated first factor accounted for 57% of the total variance. These results compare favorably with those of the American brain-damaged sample tested with the WAIS-R. For these patients, the loadings ranged from a low of .41 on Digit Span to a high of .82 on Similarities. The unrotated first factor accounted for 49% of the total variance. Table 3 presents the two-factor solutions after varimax rotation for the Chinese and American samples. Within the Chinese group, factor I was composed of the six verbal subtests, accounted for 37.5% of the total variance, and had an eigenvalue of 6.59. Factor I1 consisted of the five Performance subtests, accounted for 30.4% of the total
X. DAI
110
et
rrl.
TABLE 3 Two-Factor Solutions for Chinese and American Brain-Damaged Subjects
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
Chinese
American
Subtest
I
11
I
11
Information Digit Span Vocabulary Arithmetic Comprehension Similarities Picture Completion Picture Arrangement Block Design Object Assembly Digit Symbol
.84
.34 .35 .33 .38 .06 .38 .66 .86 .74 .I2 .68
.29 .30 .08 .39 .35 .56 .78 .82 .87 .I4 .76
.I4
.57 .76 .77 .85 .76 .5l .32 .42 .23 .I2
.29 .93 .35 .72 .61 .26 .23 .I6 .29 .28
variance, and had an eigenvalue of 1.50. These results are generally consistent with Wechsler’s (198 I ) designation of Verbal and Performance IQs and simultanteously demonstrate the well known Verbal-Comprehension (VC) and Perceptual-Organization (PO) factors that regularly emerge in studies of the WAIS-R (Ryan & Sattler, 1988). The American brain-damaged group also displayed clearcut VC and PO factors, but the order of extraction was reversed. Nevertheless, the coefficient of congruence calculated between the VC factors for the Chinese and American subjects was .94. The coefficient of congruence was .97 across groups on the PO factor. These results indicate that the two-factor solution for the Chinese brain-damaged patients is highly similar to that of the American sample with confirmed neurological damage involving the brain. For both groups, the three factor solutions following varimax rotation appear in Table 4. Within the Chinese sample, factor I accounted for 32.6% of the total variance, had an eigenvalue of 6.33, and corresponds to the well known VC construct. Factor I1 accounted for 29.5% of the total variance, had an eigenvalue of 1.17, and corresponds to the Performance Scale, with all PO subtests loading at .64 or greater. TABLE 4 Three-Factor Solutions for Chinese and American Brain-Damaged Subjects Chinese
American
Subtest
I
I1
111
Information Digit Span Vocabulary Arithmetic Comprehension Similarities Picture Completion Picture Arrangement Block Design Object Assembly Digit Symbol
.8 I
.34 .29 .33 .32 .06 .39 .64 .87 .72 .74 .66
.24 .57 .20 .57 .21 .I3 .3 I .I3 .25 .04 .22
.42 .I3 .63 .83 .80 .44 .30 .31
.23 .06
I
I1
111
.2 I
.71 .I6 .96 .21 .66 .51 .23 .21 .I2 .29 .I3
.I7 .59 .I3 .I1 .29 .21 .I8
.I6
.09 .24 .33 .56 .I7 .81 .83 .79 .69
.I8 ,215 .07 .35
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
WAIS-RC FACTOR ANALYSIS
111
Factor I11 was less clearly defined than the preceding two, was composed of the factorially complex Digit Span and Arithmetic subtests, and accounted for 9.3% of the total variance. The associated eigenvalue was only .31. This factor resmembles the Freedom From Distractibility (FFD) construct discussed by Parker (1 983). However, inspection of Table 4 suggests that a three factor solution may represent over-factoring of the WAIS-RC for neurologically impaired subjects. Additional research with larger samples of Chinese patients is needed to clarify this possibility. Nevertheless, comparison of the appropriate Chinese factors with those reported by Ryan and Schneider yielded coefficients of congruence that were impressively high: .93, .98, and .97, respectively, for VC, PO, and FFD. From a statistical point of view, the three factor solutions for the Chinese and American samples are equivalent. These findings demonstrate substantial cross-cultural congruence for Chinese and American brain-damaged samples and suggest that the WAIS-RC measures essentially the same constructs as the WAIS-R. Nevertheless, there were subtle differences between the groups. For the Chinese, the VC factor was extracted first; for the Americans the PO factor emerged first. Also, the Chinese data argued for a two-factor solution, while a three-factor interpretation appeared justified in the American sample. Perhaps these differences are due, at least in part, to the unique nature of the Chinese sample, the relatively small number of oriental subjects, and/or the subtle effects of translation and modification on individual test items. Further research is needed to clarify whether or not these differences have any clinical significance. REFERENCES Dai, X. Y., Gong, Y. X. & Zhong, L. (1990). Factor analysis of the mainland Chinese version of the Wechsler Adult Intelligence Scale. Psychological Assessment: A Journal of Consulting and Clinical Psychology, 2, 31-34. Gong, Y. X. (1982). Manua1,forthe Wechsler Adult Intelligence Scale: Chinese Revision. Changsha, Hunan, China: Hunan Medical College. Gutkin, T. B., Reynolds, C . R., & Galvin, G. A. (1984). Factor analysis of the Wechsler Adult Intelligence Scale-Revised (WAIS-R): An examination of the standardization sample. Journal of School Psychology, 22, 83-93. Matarazzo, J. D. (1972). Wechsler's measurement and appraisal of adult intelligence (5th ed.). New York: Oxford University Press. Parker, K. (1983). Factor analysis of the WAIS-R at nine age levels between 16 and 74 years. Journal of Consulting and Clinical Psychology, 51, 302-308. Ryan, J. J. & Sattler, J. M. (1988). Wechsler Adult Inteligence Scale-Revised (WAIS-R). In J. M. Sattler, Assessment cf children (3rd ed.). San Diego: Sattler. Ryan, J. J. & Schneider, J. A. (1986). Factor analysis of the Wechsler Adult Intelligence Scale-Revised (WIS-R) in a brain-damaged sample. Journal of Clinical Psychology, 42, 962-964. Wechsler, D. (1955). Manual for the Wechsler Adult intelligence Scale. New York: The Psychological Corporation. Wechsler, D. (198 1). WAIS-R manual. New York: The Psychological Corporation.
J . Neuroscience, 1990, Vol. 55, pp. 107-1 I 1 Reprints available directly from the publisher Photocopying permitted by license only Intern.
and Breach Science Publishers S.A. Printed in the United Kingdom
Brief Communication FACTOR ANALYSIS OF THE MAINLAND CHINESE VERSION OF THE WECHSLER ADULT INTELLIGENCE SCALE (WAIS-RC) IN A BRAINDAMAGED SAMPLE XIAOYANG DAT
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
Psychological Research Unit, Hunan Medical University, Changsha, People’s Republic of China
JOSEPH J. RYAN and ANTHONY M. PAOLO Dwight D . Eisenhower Department of Veterans Aflairs Medical Center Leavenworth, Kansas, USA
ROBERT G. HARRINGTON University of’ Kansas, Lawrence, Kansas, USA (Received May 17, 1990) We factor analyzed the Chinese revision of the Wechsler Adult Intelligence Scale (WAIS-RC) in a sample of 59 individuals with medically diagnosed brain damage. The Chinese subjects consisted of 42 males and 17 females with means for Verbal, Performance, and Full Scale IQ of 83.88 (SD = 22.11), 75.49 (SD = 20.63), and 78.42 ( S D = 21.97), respectively. Clear support was found for a general intelligence factor (g) and the Full Scale IQ. Similarly, the two-factor solution provided support for Wechsler’s (1981) Verbal and Performance IQ designations. The three-factor solution revealed the familiar VerbalComprehension and Perceptual-Organization factors. However, the Freedom From Distractibility factor was less clearly defined. Comparisons of Chinese and American factor structures for neurologically impaired persons demonstrated high coefficients of congruence, ranging from .93 to .98. Overall, the findings demonstrated substantial congruence cross culturally for Chinese and American brain-damaged samples and suggest that the WAIS-RC measures essentially the same constructs a s the WAIS-R. Keywords: Brain damage. WAIS-RC, Factor analysis
The Wechsler Adult Intelligence Scale (WAIS; Wechsler, 1955) has been translated, modified, and standardized for application within the People’s Republic of China. The new test, which is known as the Wechsler Adult Intelligence Scale-Revised for China (WAIS-RC; Gong, 1982), has been widely used in medical and educational settings. The WAIS-RC consists of 1 1 subtests and maintains Wechsler’s logic-based Verbal-Performance dichotomy. Factor analytic studies of the Chinese standardization sample (Dai, Gong, & Zhong, 1990) indicate that the WAIS-RC factor structure and variance components are highly similar to those of the American WATS and Wechsler Adult Intelligence Scale-Revised (WAIS-R; Wechsler, 1981). These findings
Requests for reprints should be sent to Joseph J. Ryan, Chief, Psychology Service (1 16B). DDE DVA Medical Center, Leavenworth, KS66048.
107
X . DAI t t
I08
trl
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
suggest that factor-based clinical interpretations previously established for the WAIS and WAIS-R (Matarazzo, 1972; Parker, 1983) may generalize to the WAIS-RC. Dai et al. (1990) reported that the WAIS-RC is frequently used in the assessment of persons with suspected or confirmed brain disorders. However, there are no published studies which elucidate the factor structure of the scale within a neurologically comprised sample. The present investigation was intended to rectify this situation by reporting the results of a principal-factor analysis of the WAIS-RC in a diagnostically heterogeneous group of brain-impaired individuals. The second purpose of the study was cross-cultural and compared the WAIS-RC structure with that of an American sample of brain-damaged patients tested with the WAIS-R (Ryan & Schneider, 1986). METHOD Subjec t.7
The sample consisted of 59 neurology inpatients from three medical school affiliated hospitals located in the southwestern region of the People’s Republic of China. For each subject, brain-damage was diagnosed by a team of physicians based on the results of a medical history, neurological examination, and at least one of the following: Computed axial tomography scan, angiogram, or neurosurgical report. Seven patients had left hemisphere damage, seven had right hemisphere lesions, and 45 were considered to have bilateral brain damage. Table 1 provides demographic information on the sample in terms of age, sex distribution, and education. Means and standard deviations on the WAIS-RC subtests and IQs appear in Table 2.
TABLE 1 Demographic Characteristics of the Chinese Brain-Damaged Sample Variable
n
%
Sex Male Fcmalc
42
11.2 28.8
17
Age
1.7 3.4 15.3 10.2 20.3 16.9 23.1
> 65
1 2 9 6 12 10 14 5
Education 0- 3 4- 8 9 II 12-14 > 15
5 19 20 6 9
8.5 32.2 33.9 10.2 15.3
16-17 18-19 20-24 25-34 35-44 45-54 55-64
8.5
WAIS-RC FACTOR ANALYSIS
109
TABLE 2 Means and Standard Deviations for WAIS-RC 1Qs and Subtest Scores
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
Variables Information Digit Span Vocabulary Arithmetic Comprehension Similarities Picture Completion Picture Arrangement Block Design Object Assembly Digit Symbol Verbal IQ Performance IQ Full Scale IQ
Mean
SD
8.00 7.86 7.51 6.66 8.20 6.59 5.63 5.61 6.36 6.19 6.00
3.91 3.55 3.52 4.22 4.0 1 3.64 3.04 3.83 3.20 3.44 3.23
83.88 75.49 78.42
22.11 20.63 21.97
Procedure
Each examination was conducted by a member of the National Psychological Testing Coworker Group of China from 1981 to 1985. All 11 subtests of the WAIS-RC were administered to each patient by a trained examiner according to standardized instructions (Gong, 1982). Intercorrelations of scaled scores on the WAIS-RC subtests were obtained and subjected to a principal-factor analysis with iterations (squared multiple correlations in the diagonal) followed by varimax rotation of two- and three-factors. The degree of similarity between orthogonal factors for the WAIS-RC and those from the Ryan and Schneider (1986) study was assessed with the coefficient of congruence. Since Ryan and Schneider reported only a three-factor solution in their original paper, it was necessary to reanalyze their data so that a two-factor solution was also available for comparison with the Chinese sample. RESULTS AND DISCUSSION Following Gutkin, Reynolds, and Galvin (1984), subtest loadings on the first unrotated factor of the two-factor solution were taken as measures of each subtest’s relationship with general intelligence (8). For the Chinese subjects, there was clear support for a robust g factor and the validity of the Full Scale IQ. Every subtest displayed a sizable loading on the first unrotated factor with values ranging from a low of .53 on the Digit Span to a high of .80 on Block Design and Picture Arrangement. The unrotated first factor accounted for 57% of the total variance. These results compare favorably with those of the American brain-damaged sample tested with the WAIS-R. For these patients, the loadings ranged from a low of .41 on Digit Span to a high of .82 on Similarities. The unrotated first factor accounted for 49% of the total variance. Table 3 presents the two-factor solutions after varimax rotation for the Chinese and American samples. Within the Chinese group, factor I was composed of the six verbal subtests, accounted for 37.5% of the total variance, and had an eigenvalue of 6.59. Factor I1 consisted of the five Performance subtests, accounted for 30.4% of the total
X. DAI
110
et
rrl.
TABLE 3 Two-Factor Solutions for Chinese and American Brain-Damaged Subjects
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
Chinese
American
Subtest
I
11
I
11
Information Digit Span Vocabulary Arithmetic Comprehension Similarities Picture Completion Picture Arrangement Block Design Object Assembly Digit Symbol
.84
.34 .35 .33 .38 .06 .38 .66 .86 .74 .I2 .68
.29 .30 .08 .39 .35 .56 .78 .82 .87 .I4 .76
.I4
.57 .76 .77 .85 .76 .5l .32 .42 .23 .I2
.29 .93 .35 .72 .61 .26 .23 .I6 .29 .28
variance, and had an eigenvalue of 1.50. These results are generally consistent with Wechsler’s (198 I ) designation of Verbal and Performance IQs and simultanteously demonstrate the well known Verbal-Comprehension (VC) and Perceptual-Organization (PO) factors that regularly emerge in studies of the WAIS-R (Ryan & Sattler, 1988). The American brain-damaged group also displayed clearcut VC and PO factors, but the order of extraction was reversed. Nevertheless, the coefficient of congruence calculated between the VC factors for the Chinese and American subjects was .94. The coefficient of congruence was .97 across groups on the PO factor. These results indicate that the two-factor solution for the Chinese brain-damaged patients is highly similar to that of the American sample with confirmed neurological damage involving the brain. For both groups, the three factor solutions following varimax rotation appear in Table 4. Within the Chinese sample, factor I accounted for 32.6% of the total variance, had an eigenvalue of 6.33, and corresponds to the well known VC construct. Factor I1 accounted for 29.5% of the total variance, had an eigenvalue of 1.17, and corresponds to the Performance Scale, with all PO subtests loading at .64 or greater. TABLE 4 Three-Factor Solutions for Chinese and American Brain-Damaged Subjects Chinese
American
Subtest
I
I1
111
Information Digit Span Vocabulary Arithmetic Comprehension Similarities Picture Completion Picture Arrangement Block Design Object Assembly Digit Symbol
.8 I
.34 .29 .33 .32 .06 .39 .64 .87 .72 .74 .66
.24 .57 .20 .57 .21 .I3 .3 I .I3 .25 .04 .22
.42 .I3 .63 .83 .80 .44 .30 .31
.23 .06
I
I1
111
.2 I
.71 .I6 .96 .21 .66 .51 .23 .21 .I2 .29 .I3
.I7 .59 .I3 .I1 .29 .21 .I8
.I6
.09 .24 .33 .56 .I7 .81 .83 .79 .69
.I8 ,215 .07 .35
Int J Neurosci Downloaded from informahealthcare.com by McMaster University on 11/24/14 For personal use only.
WAIS-RC FACTOR ANALYSIS
111
Factor I11 was less clearly defined than the preceding two, was composed of the factorially complex Digit Span and Arithmetic subtests, and accounted for 9.3% of the total variance. The associated eigenvalue was only .31. This factor resmembles the Freedom From Distractibility (FFD) construct discussed by Parker (1 983). However, inspection of Table 4 suggests that a three factor solution may represent over-factoring of the WAIS-RC for neurologically impaired subjects. Additional research with larger samples of Chinese patients is needed to clarify this possibility. Nevertheless, comparison of the appropriate Chinese factors with those reported by Ryan and Schneider yielded coefficients of congruence that were impressively high: .93, .98, and .97, respectively, for VC, PO, and FFD. From a statistical point of view, the three factor solutions for the Chinese and American samples are equivalent. These findings demonstrate substantial cross-cultural congruence for Chinese and American brain-damaged samples and suggest that the WAIS-RC measures essentially the same constructs as the WAIS-R. Nevertheless, there were subtle differences between the groups. For the Chinese, the VC factor was extracted first; for the Americans the PO factor emerged first. Also, the Chinese data argued for a two-factor solution, while a three-factor interpretation appeared justified in the American sample. Perhaps these differences are due, at least in part, to the unique nature of the Chinese sample, the relatively small number of oriental subjects, and/or the subtle effects of translation and modification on individual test items. Further research is needed to clarify whether or not these differences have any clinical significance. REFERENCES Dai, X. Y., Gong, Y. X. & Zhong, L. (1990). Factor analysis of the mainland Chinese version of the Wechsler Adult Intelligence Scale. Psychological Assessment: A Journal of Consulting and Clinical Psychology, 2, 31-34. Gong, Y. X. (1982). Manua1,forthe Wechsler Adult Intelligence Scale: Chinese Revision. Changsha, Hunan, China: Hunan Medical College. Gutkin, T. B., Reynolds, C . R., & Galvin, G. A. (1984). Factor analysis of the Wechsler Adult Intelligence Scale-Revised (WAIS-R): An examination of the standardization sample. Journal of School Psychology, 22, 83-93. Matarazzo, J. D. (1972). Wechsler's measurement and appraisal of adult intelligence (5th ed.). New York: Oxford University Press. Parker, K. (1983). Factor analysis of the WAIS-R at nine age levels between 16 and 74 years. Journal of Consulting and Clinical Psychology, 51, 302-308. Ryan, J. J. & Sattler, J. M. (1988). Wechsler Adult Inteligence Scale-Revised (WAIS-R). In J. M. Sattler, Assessment cf children (3rd ed.). San Diego: Sattler. Ryan, J. J. & Schneider, J. A. (1986). Factor analysis of the Wechsler Adult Intelligence Scale-Revised (WIS-R) in a brain-damaged sample. Journal of Clinical Psychology, 42, 962-964. Wechsler, D. (1955). Manual for the Wechsler Adult intelligence Scale. New York: The Psychological Corporation. Wechsler, D. (198 1). WAIS-R manual. New York: The Psychological Corporation.
