go through a list of colored shapes and mark
the targeted shapes. This is a supplementary
subtest for IQ scores.Obtaining the Full Scale IQ Score and Index
Scores. Raw scores from each subtest are con-
verted to scaled scores—standardized scores for a
given age group. The Full Scale IQ and Index scores
are then computed by adding together scaled scores
from select subtests and converting these sums to IQ
equivalents. The supplemental subtest scores are only
used in these calculations if they were used to substi-
tute for one or more of the core subtests. Table 7-4
lists the WAIS-IV subtests that are used to calculate
the Full Scale IQ and each of the Index scores: Ver-
bal Comprehension, Perceptual Reasoning, Work-
ing Memory, and Processing Speed.
Standardization. The WAIS-IV was standard-
ized on a sample of 2,200 adults, including equal
numbers of men and women in each of 13 age
groups ranging from age 16 to 90 years. The sample
was stratified according to age, sex, race/ethnicity,
education level, and geographic regions using 2005
U.S. Census Bureau data as a guide.
Reliability and Validity. The average Full Scale
IQ split-half reliability coefficient across age groups
was .98, and the average split-half reliability coeffi-
cients across age groups for the Verbal Comprehen-
sion, Perceptual Reasoning, Working Memory,
and Processing Speed Index scores range from .90
to .96. Test–retest reliabilities over an average of
three weeks range from .74 to .90 across age groups
for the various subtests.
Data support the validity of WAIS-IV scores
(Wechsler, 2008). Relevant subtest scores from
other tests of cognitive ability (e.g., the WAIS-III and
WISC-IV) are significantly correlated with targeted
subscale scores derived from the new WAIS-IV.
For example, the WAIS-IV Working Memory
Index is highly correlated with scales from other
measures tapping attention and concentration, and
the WAIS-IV Verbal Comprehension Index corre-
lates significantly with scores from external measures
of language fluency and language comprehension.
Finally, as further support for the factorial validity of
the WAIS-IV, a series of exploratory and confirma-
tory factor analyses largely supported the predicted
four factors of the WAIS-IV (Verbal Comprehen-
sion, Perceptual Reasoning, Working Memory, and
Processing Speed) as well as the predicted associations
between the WAIS-IV subtests and these factors.
This case example demonstrates how an over-
reliance on global IQ scores (Full Scale IQ) can be
misleading. Although Mr. Ryan’s global scores
were in the average range, a more in-depth exami-
nation of his individual subtest scores and Index
scores suggests cognitive limitations. For this reason,
it is important to calculate and interpret discrepan-
cies among subtest scores, Full Scale IQ score, and
Index scores to give a rich clinical picture of exam-
inees’cognitive abilities.The WISC-IV
The Wechsler Intelligence Scale for Children
(WISC) was first developed in 1949, revised in 1974
(WISC-R), and again in 1991 (WISC-III; Wechsler,
1991). The latest version, theWechsler Intelligence
Scale for Children Fourth Edition (WISC-IV),waspub-
lished in 2003 (Wechsler, 2003). Appropriate forF I G U R E 7-5 Simulated item from the WAIS-IV
Picture Completion subtest.
SOURCE: Simulated item similar to those found in Wechsler Adult Intelli-
gence Scale(R), Fourth Edition (WAIS-IV) Copyright (c) 2008 NCS Pearson,
Inc. Reproduced with permission. all rights reserved.“Wechsler Adult Intelli-
gence Scale”and“WAIS”are trademarks, in the US and/or other countries,
of Pearson Education, Inc. or its affiliate(s).
THE ASSESSMENT OF INTELLIGENCE 209