Actually, you can calculate your own (non-extended) GAI by summing up the scores (not the percentile ranks) of Block Design, Picture Concepts, Matrix Reasoning, Similarities, Vocabulary, and Comprehension and then refer to the chart here:

http://images.pearsonclinical.com/images/assets/WISC-IV/80720_WISCIV_Hr_r4.pdf

If I read this correctly, there isn't a significant statistical difference between the two scores.

Last edited by George C; 07/24/15 01:48 PM.