Reliability and Validity. Wechsler (2003) re-
ported that the average (across age groups) split-
half reliabilities for the Verbal Comprehension
Index, Perceptual Reasoning Index, Working Mem-
ory Index, Processing Speed Index, and Full Scale of
the WISC-IV were .94, .92, .92, .88, and .97,
respectively. The average split-half reliabilities for
the individual subtests ranged from .70 to .90. The
test–retest reliabilities (mean interval between testing
= 32 days) across three different age groups were all
fairly high. As for validity, WISC-IV scores are
highly correlated with scores from other measures
of intelligence (e.g., the WISC-III). Further, results
from a series of studies in which the WISC-IV was
administered to several special groups of children
(e.g., gifted children, children with learning disabil-
ities, children with motor impairment) were gener-
ally consistent with expectations, given prior research
on these populations and given the content of the
WISC-IV subtests and indices (Wechsler, 2003).
Finally, initial factor analyses reveal that four
factors (corresponding to the VCI, PRI, WMI,
and PSI) account for the relations among the 15
subtest scores. Therefore, these analyses support
the theoretical model and organization of the
WISC-IV (Wechsler, 2003).
The WPPSI-III
The Wechsler Preschool and Primary Scale of Intel-
ligence (WPPSI) was developed in 1967, followed by
the WPPSI-II in 1989 and the current WPPSI-III in- The scale is quite similar to the WISC-IV but
geared specifically towards the assessment of intellec-
tual ability among much younger youth. Two sets of
subscales are included. One set is designed for youth
ages 2 years, 6 months to 3 years, 11 months; a sec-
ondsetofsubscalesisdesignedforyouthages4years
to 7 years, 3 months.
At present, the WPPSI-III yields only three
indices, the Full Scale IQ, Verbal IQ, and Perfor-
mance IQ. For youth ages 4 years and older, the
WPPSI also yields a Processing Speed Index. Ver-
sions of many of the same subscales used in the
WAIS and the WISC tests also are used in the
WPPSI (e.g., Information, Block Design, Object
Assembly, Coding, Matrix Reasoning, etc). The
WPPSI-III also includes several subscales designed
specifically for younger children (e.g., Receptive
Vocabulary, Word Reasoning, Picture Concepts).
Standardization, Reliability, and Validity. Data
used to standardize the WPPSI-III included 1,700
children between the ages of 2 years, 6 months and
VCI
Similarities
Vocabulary
Comprehension
Information
Word ReasoningWMIDigit Span
Letter-Number
Sequencing
ArithmeticPRIBlock Design
Picture Concepts
Matrix Reasoning
Picture CompletionPSICoding
Symbol Search
CancellationFSIQF I G U R E 7-6 Organization of the WISC-IV.
NOTE: Supplemental subtests are shown in italics.
SOURCE: Text describing organization of the Wechsler Intelligence Scale for Children, Fourth Edition (WISC-IV). Copyright (c) 2003 NCS Pearson, Inc. Repro-
duced with permission. All rights reserved.“Wechsler Intelligence Scale for Children”and“WISC”are trademarks, in the US and/or other countries, of
Pearson Education, Inc. or its affiliate(s).
Wechsler Intelligence Scale for Children: Fourth Edition. Copyright© 2003 by Harcourt Assessment, Inc. Reproduced by permission.All right reserved.212 CHAPTER 7