I'm not seeing the data from the study this book is citing, but there is this quote in the book
WISC-IV: Clinical Assessment and Intervention (2008) that would indicate the potential for a high score on a group test but not on an individual test,
Of note in the standardization sample is the large number of students previously identified as gifted who are not performing two standard deviations above the mean on any factor of the WISC-IV. It is unclear if this discrepancy is a product of the considerable changes to both the content and structure from the WISC-III to the WISC-IV, or if there being a large number of students (29%) who are included in the WISC-IV gifted sample based solely on a group-administered cognitive ability test that offers a less valid measure of abilities than an individually administered one.
Ch. 8: The Use of the WISC-IV in Assessment and Intervention Planning for Children Who are Gifted, pg. 223 (
http://books.google.com/books?hl=en...XfD1k5cUBFdXWyqL9XYQ#v=onepage&q&f=false)
Of course, as they mentioned, it could just be that the changes to the test from version III to version IV changed who was performing in the gifted range. It would have been nice if they stratified the data and looked at how the scores lined up btwn version III to version IV for kids who had taken both and not just lumped kids with gifted scores on on the WISC-III in with kids with gifted scores on group tests.
eta: there is this interesting bit of info as well - while the GDC has a self selected sample group, the group they tested on the WISC-IV when looking at its validity as a new test, got higher scores on the g loaded subtests than did the gifted group in the norming group whereas the gifted norming group did better on the speed related items than did the GDC gifted group.
WISC-IV Subtest Means of 63 Gifted Children
in the Norm Sample compared with 103 Gifted Children from GDC
Gifted Norm Group - Similarities: 14.10
GDC - Similarities: 15.8
Gifted Norm Group - Vocabulary: 14.60
GDC - Vocabulary: 15.4
Gifted Norm Group - Comprehension: 14.10
GDC- Comprehension: 14.8
Gifted Norm Group - Matrix Reasoning: 13.40
GDC - Matrix Reasoning: 14.7
Gifted Norm Group - Picture Concepts: 12.70
GDC - Picture Concepts: 14.6
Gifted Norm Group - (Arithmetic): 14.20
GDC - (Arithmetic): 14.1
Gifted Norm Group - (Information): 13.90
GDC - (Information): 14.1
Gifted Norm Group - Block Design: 13.80
GDC - Block Design: 13.2
Gifted Norm Group - (Word Reasoning): 13.20
GDC - (Word Reasoning): 12.9
Gifted Norm Group - Letter-Numb. Sequencing: 12.60
GDC - Letter-Numb. Sequencing: 12.9
Gifted Norm Group - (Picture Completion): 13.00
GDC - (Picture Completion): 12.5
Gifted Norm Group - Symbol Search: 12.10
GDC - Symbol Search: 11.5
Gifted Norm Group - Digit Span: 12.00
GDC - Digit Span: 12.3
Gifted Norm Group - (Cancellation): 11.00
GDC - (Cancellation): 10.3
Gifted Norm Group - Coding: 11.50
GDC - Coding: 9.9
(WISC-IV Technical Manual, p. 77)
