Relationship of scores on the Wechsler preschool and primary scale of intelligence and the stanford-binet intelligence scale form LM

Journal of School Psychology 1971 • Vol. 9, No. 3

RELATIONSHIP OF SCORES ON THE WECHSLER PRESCHOOL A N D P R I M A R Y SCALE OF INTELLIGENCE A N D THE STANFORD-BINET INTELLIGENCE SCALE FORM LM NANETTE

S. P R O S S E R

University of Toledo VEDA

B. C R A W F O R D

Bowling Green State University

Summary: A preschool sample of 25 boys and 25 girls (mean age, 58 months) was administered the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) and the Stanford-Binet Form LM (SB). WPPSI Verbal, Performance, and Full Scale IQ scores correlated .84, .60, and .82 respectively with the SB IQ scores. In spite of this high positive relationship, WPPSI and SB scores were not interchangeable. The Full Scale WPPSI consistently yielded lower IQs than did the SB (p < .01). WPPSI correlations with the SB and WPPSI subtest correlations with the three WPPSI scales closely followed the same pattern as the respective Wechsler Intelligence Scale for Children correlations at an older age level. Girls scored higher than boys on the Verbal Scale (p < .02) and on the Full Scale (p < .05). Psychological evaluations of preschool and primary children have been increasingly emphasized within the last decade. In some states, testing for early entrance into school is a requirement which must be met by the school psychologist or some other designated examiner. A decision on the child's probable success in school is necessary. In addition, educators are interested in early recognition of learning disabilities. This study investigated the relationship between the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) (Wechsler, 1967) and the Stanford-Binet Intelligence Scale Form LM (SB) (Terman & Merrill, 1960), and compared the WPPSI to the Wechsler Intelligence Scale for Children (WlSC) (Wechsler, 1 9 4 9 ) a s a downward extension of that scale. METHOD

The 50 Ss were 25 boys and 25 girls randomly selected from a suburbart middle class preschool population who would be eligible to enter kindergarten in the following September. The Ss ranged in age from 50 months to 67 months, with a mean age of 58 months. Each S was given both tests, by one of two female examiners within a five day period, except for two Ss who completed the testing within a three-week period. Order of presentation was randomly determined. Journal o f S c h o o l ?sycholoL'F, V o l u m e

9, 1971 278

Relationship of Scores on the WPPSI and S-B (LM)

279

RESULTS

Table 1 shows the ranges, means, and standard deviations (s.d.) of SB IQ scores, WPPSI Verbal, Performance, and Full Scale IQ scores, and the scaled scores of each WPPSI subtest. WPPSI Full Scale IQ scores ranged from a low of 76 to a high of 129; SB IQ scores ranged from a low of 73 to a high of 144. Both test means were considerably above the general population mean of 100, probably reflecting the middle class suburban population from which the sample was drawn. The mean WPPSI Full Scale IQ score of 105.1 was 7.5 points lower than the SB IQ mean of 112.6 (p < .01). The WPPSI s.d. of 12.8 was smaller than the standardization sample s.d. of 15 as would be expected in the more homogeneous population. The SB s.d. of 15.1 approached the standardization sample s.d. of 16. Figure 1 is a scattergram which shows the distribution of WPPSI and SB IQ scores. Discrepancy between an S's WPPSI and SB IQ scores increased directly with level of intelligence; none of the eight subjects with SB IQ scores in the very superior range (130 and above) earned WPPSI IQ scores in the same range. In this respect, the distribution of scores on the WPPSI appeared to follow the same pattern as the WlSC, as noted by Harlow, Price, Tatham, & Davidson (1957). Table 2 compares the means and s.d. of boys' and girls' WPPSI IQ scores and subtest scaled scores. The girls' WPPSI Verbal IQ mean of 105.8 was 9.6 points higher than the boys' Verbal IQ mean of 96.2 (p < .02); girls' Table 1 WPPSI and SB Ranges, Means, and Standard Deviations Test

Range

Mean

Standard Deviation

Wechsler Preschool and Primary Scale of Intelligence Scaled Scores Information Vocabulary Arithmetic Similarities Comprehension Animal House Picture Completion Mazes Geometric Design Block Design

3-15 3-18 4-16 4-15 3-14 4-16 6-18 3-16 6-17 8-19

10.0 10.7 10.5 9.5 10.2 11.3 10.9 11.1 10.9 12.1

2.5 3.2 2.6 2.8 2.6 2.8 2.6 2.7 3.0 2.4

WPPSI IQ Scores Verbal Performance Full Scale

59-125 85-135 76-129

101.0 108.7 105.1

13.5 12.4 12.8

Stanford-Binet (Form L-M) IQ Scores

73-144

112.6

15.1

JournAl of S c h o o l Psychology, V o l u m e 9, 19'/1

N. S. Prosser a n d V. B. C r a w f o r d

280

Figure 1 Distribution of WPPSI and SB IQ Scores of 50 Preschool Children WPPSI 40 49

50 59

60 69

70 79

80 89

90 99

100 109

110 119

120 129

140-149

1

130-139

uq

1

4

2

120-129

1

3

1

4

110-119

2

5

4

1

6

2

100-109

2

3

90-99

2

3

80-89

2

70-79

1

60-69 50-59 40-49

Table 2 A Comparison of Boys' and Girls' WPPSI Scores Test

Boys Mean

Gkls SD

Mean

SD

Scaled Scores Information Vocabulaxy Arithmetic Similarities Comprehension Animal House Picture Completion Mazes Geometric Design Block Design

9.3 10.1 9.4 9.1 9.1 10.3 10.9 11.6 10.4 11.5

2.7 2.8 2.4 3.2 2.4 3.0 2.8 2.9 2.9 2.2

10.7 11.4 I 1.5 9.9 11.3 12.4 10.9 10.7 11.4 12.8

2.1 3.5 2.4 2.4 2.2 2.2 2.4 2.5 3.1 2.6

IQ Scores Verbal Scale Performance Scale Full Scale

96.2 106.3 101.2

13.8 13.1 12.8

105.8 III.I 109.1

I 1.6 11.5 11.7

Journal o f S c h o o l Psychology, V o l u m e 9, 1 9 7 1

130 139

140 149

Relationship of Scores on the WPPSI and S-B (LM)

281

Performance IQ mean of 111.1 was 4.8 points higher than the boys' mean of 106.3 (p < .20). The girls' mean IQ score of 109.1 on the Full Scale was 7.9 points higher than the boys' mean of 101.2 (p < .05). Girls tended to score higher than boys on each subtest except for two Performance subtests. Boys and girls scored the same on Picture Completion and boys tended to score higher than girls on Mazes. This pattern of sex difference in scoring on the Performance tests was discussed by Herman (1968). Table 3 shows that correlations of WPPSI scores with SB scores followed the same pattern as WlSC and SB correlations found by Harlow et al. (1957). WPPSI Verbal subtest scores correlated higher with the SB than did the Performance subtest scores. Table 4 shows that the intercorrelations of tests in the WPPSI followed closely the same pattern as WISC intercorrelations given at an age level with high subtest and Full Scale reliabilities (Wechsler, 1949, p. 12). DISCUSSION The high positive relationships between WPPSI Verbal and Full Scale IQs and SB IQs, and the moderate positive relationship between the WPPSI Performance IQs and SB IQs indicated that to a considerable degree all four scales seemed to measure the same factors. However, because the WPPSI Full Scale IQ test in general yielded lower IQ scores than did the SB, the two test scores were not interchangeable. The probability of predicting superior or very superior SB IQ scores from superior WPPSI IQ scores was very high.

Table 3 Coefficients of Correlation of WPPSI Scaled Scores and IQ Scores with SB IQ Scores Test

SB IQ

WPPSI

r

Scaled scores Information Vocabulary Arithmetic Similarities Comprehension Animal House Picture Completion

.72 .74 .69 .59 .57 .51 .47

Mazes

.13

Geometric Design Block Design

.39 .53

IQ Scores Verbal Performance Full Scale Journal o f S c h o o l Psychology, V o l u m e 9, 1 9 7 1

.84 .60 .82

282

N.S.

Prosser a n d V. B. C r a w f o r d

Table 4 lntercorrelation of Tests in the WPPSI Compared with the lntercorrelation of Tests in the WlSC Test

WPPSI (N=50)

Test

VS r

Information Vocabulary Arithmetic Similarities Comprehension Animal House Picture Completion Mazes Geometric Design Block Design

.73 .74 .66 .59 .70 .50 .47 .19 .25 .56

Verbal Scale Performance Scale

Mean Age 5 PS FSS r r .52 .54 .51 .35 .35 .41 .64 .41 .55 .61

.65 .66 .60 .46 .55 .43 .55 .24 .32 .61

.58

.90 .87

WlSC (N=200) a VS r

Age 13V2 PS FSS r r

.80 .75 .59 .74 .68 .42 b .38

.51 .51 .38 .52 .37 .42 b .55

.73 .70 .55 .71 .58 .48 h .51

.50

.65

.64

.56

.89 .87

Note. When a single test was correlated with a composite of which it also was a contributing member, it was necessary to correct the r for spuriousness (McNemar, 1949, p. 139). a Wechsler, D. Wechsler Intelligence Scale for Children. New York: The Psychological Corporation, 1949. P. 12. b These correlations are for the Coding subtest in the WISC. H o w e v e r , p r e d i c t i o n o f s u p e r i o r WPPSI IQ scores f r o m s u p e r i o r or ve~ s u p e r i o r SB IQ scores was n o t justified. T h e a d e q u a c y o f the SB n o r m s for t o d a y ' s m i d d l e class p r e s c h o p o p u l a t i o n m i g h t be q u e s t i o n e d in view o f t h e significant d i f f e r e n c e betwe~ t h e SB m e a n a n d t h e WPPSI m e a n s f o u n d in this s t u d y . N o r m s e s t a b l i s h e d f, t h e SB m o r e t h a n a d e c a d e ago m a y n o l o n g e r b e a p p r o p r i a t e for t h e preser day p r e s c h o o l child w h o is e x p o s e d to increasing a m o u n t s o f televisio b o o k s , e d u c a t i o n a l - t y p e toys, a n d travel, m a d e possible b y o u r h i g h t e c h n o l o g i c a l society. T h e significantly higher WPPSI V e r b a l a n d Full Scale girls' m e a n s f o u n d this s t u d y differ f r o m H e r m a n ' s ( 1 9 6 8 ) findings o f n o significant differen~ o n a n y o f t h e WPPSI scales b e t w e e n b o y s a n d girls. F u r t h e r researc c o m p a r i n g b o y s ' a n d girls' scoring p a t t e r n s at t h e p r e s c h o o l level w o u l d ! meaningful. T h e WPPSI has several a d v a n t a g e s w h e n used b y t h e s c h o o l p s y c h o l o g i s t an i n s t r u m e n t for k i n d e r g a r t e n early e n t r a n c e evaluations. A l t h o u g h a n I score could be o b t a i n e d in a s h o r t e r p e r i o d o f t i m e using t h e SB (25-2 m i n u t e s ) , the WPPSI ( a d m i n i s t r a t i o n t i m e , 4 5 - 5 0 m i n u t e s ) p r o v i d e d a larg, sampling o f t h e child's b e h a v i o r in a h i g h l y s t r u c t u r e d s i t u a t i o n . T h e WPP', G e o m e t r i c Design s u b t e s t provides a m e a s u r e o f v i s u a l - m o t o r - p e r c e p t u d e v e l o p m e n t as part of t h e test, m a k i n g a d d i t i o n a l e v a l u a t i o n w i t h s o n o t h e r test o f these skills u n n e c e s s a r y . W h e n used as a n i n s t r u m e n t fi J o u r n a l o f S c h o o l P s y c h o l o g y , V o l u m e 9, 1 9 7 1

Relationship of Scores on the WPPSI and S-B (LM)

283

kindergarten early entrance evaluation, however, the tendency for the WPPSI to yield lower scores than the SB should be considered. An adjustment of suggested minimum IQ levels which were established for the SB would be indicated when the WPPSI was used. Plant (1968) recommended that the WPPSI Geometric Designs and Information subtest scaled scores be added to obtain the best short-form prediction of reading achievement. Additional longitudinal studies correlating the WPPSI scales and subtests with some criteria of school achievement would be valuable. REFERENCES

Harlow, J. E., Jr., Price, A. C., Tatham, L. J., & Davidson, J. F. Preliminary study of comparison between Wechsler Intelligence Scale for Children and Form L of Revised Stanford-Binet Scale at three age levels. Journal of Clinical Psychology, 1957, 13, 72-73. Herman, D. O. A study of sex differences in the WPPSI. Proceedings of the 76thAnnual Convention of the APA, 1968, 3, 455-456. McNemar, Q. Psychological statistics. New York: John Wiley & Sons, 1949. Plant, W. T., & Southern, M. L. First grade reading achievement predicted from WPPSI and other scores obtained 18 months earlier. Proceedings of the 76th Annual Convention of the APA, 1968, 3, 593-594. Terman, L. M., & Merrill, M. A. Manual for the Stanford-Binet intelligence scale form LM. Boston: Houghton Mifflin Company, 1960. Wechsler, D. Manual for the Wechsler Intelligence Scale for ChildrerL New York: Psychological Corporation, 1949. Wechsler, D. Manual for the Wechsler Preschool and Primary Scale of lntelligence. New York: Psychological Corporation, 1967. Nanette S. Prosser School Psychologist Perrysburg Public Schools Perrysburg, Ohio 43551 Veda B. Crawford School Psychologist Fulton County Schools and Wauseon Exempted Village Schools Wauseon, Ohio 43567 Received: May 25, 1970 Revision Received: November 19, 1970

Journal of S c h o o l Psychology, V o l u m e 9, 1 9 7 1