Psychology
in
the
Schools
Volume
28.
January
1991
SIGNIFICANT DIFFERENCES BETWEEN INDIVIDUAL SUBTEST SCALED
SCORES AND AVERAGE SCALED SCORES ON THE WECHSLER PRESCHOOL
AND PRIMARY SCALE OF INTELLIGENCE-REVISED
STEVEN
G.
LOBELLO
Auburn University at Montgomery
This paper presents age-referenced tables that are used
for
determining significant
differences between individual subtest scaled scores and average subtest scores on the
Wechsler Preschool
and
Primary Scale of Intelligence-Revised (WPPSI-R). The tables
provide differences required at the .05 and
.01
levels of significance between any Verbal
scale subtest and the average
of
Verbal scale subtests, any Performance scale subtest
and the average
of
Performance scale subtests, and any subtest with the average of
all subtests administered. The information presented is useful for WPPSI-R profile
analysis.
The restandardization
of
the Wechsler Preschool and Primary Scale
of
Intelligence-
Revised (WPPSI-R; Wechsler, 1989) is accompanied by the need for revision of
supplementary tables to aid examiners in test interpretation. Sattler (1988) provided tables
for determining significant differences between subtest scaled scores for
all of Wechsler’s
tests, including the Wechsler Preschool and Primary Scale of Intelligence (Wechsler,
1967). LoBello and Allen (1990) have submitted a set
of
similar tables for the WPPSI-R.
Table 13 in the WPPSI-R manual (p. 135) allows for the determination
of
signi-
ficant differences between individual subtest scaled scores and the mean subtest scaled
score for the Verbal and Performance scales, as well as the overall mean subtest scaled
score. However, the table is constructed by using the average standard error
of
measure-
ment
of
individual subtests for the entire standardization sample, which may obscure
age differences. The purpose of this paper is to provide supplementary age-referenced
tables for comparing individual subtest scaled scores with various subtest scaled score
averages.
METHOD
Data for this study were obtained from the WPPSI-R manual (Wechsler, 1989)
and are based on the standardization sample
(N
=
1,700). Table 9 (p. 128) presents
reliability coefficients and standard errors
of
measurement for all WPPSI-R subtests
according to the age of the subjects. Reliability coefficients and standard errors of
measurement are reported for a 3-year age group, and then for each age group in half-
year increments up to age
7
years. Data for a total of nine age groups are reported.
Next, the average standard error of measurement for each subtest was calculated
for three subgroups. Subjects in the first subgroup ranged in age from
3
to 4% years.
Subjects in the second subgroup were from
4% to
6
years of age. The third group con-
sisted
of
subjects between the ages of 6 and 7 years.
The formula provided by Davis (1959) was used to calculate significant differences
between individual subtest scaled scores and the various averages of subtest scaled scores.
In establishing the .05 and .01 levels of significance, the Bonferroni correction procedure
was used
to
control familywise error rate (Sattler, 1988).
Correspondence concerning this article and requests for reprints should be addressed to Steven
G.
LoBello,
Dept. of Psychology, Auburn University at Montgomery, 7300 University Drive, Montgomery, Alabama,
36117-35%.
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