Calculate the scores for the sub-tests that determine the GAI score once the child has completed the full WISC. These sub-tests are: Vocabulary Comprehension, Similarities, Block Design, Matrix Reasoning and Picture Concepts.
Add up the score for the Vocabulary Comprehension sub-test following the instructions in the WISC manual. Record the number of correct responses in the accompanying answer sheet.
Add up the score for the Similarities sub-test following the instructions in the WISC manual. Record the number of correct responses in the accompanying answer sheet.
Add up the score for the Block Design sub-test following the instructions in the WISC manual. Record the number of correct responses in the accompanying answer sheet.
Add up the score for the Matrix Reasoning sub-test following the instructions in the WISC manual. Record the number of correct responses in the accompanying answer sheet.
Add up the score for the Picture Concepts sub-test following the instructions in the WISC manual. Record the number of correct responses in the accompanying answer sheet.
Add up all the scores and record in the WISC answer sheet once you have scored each of the sub-tests involved in the GAI score. You now have your GAI raw score which you need to convert into a percentage.
Locate the General Ability Sum of Scaled Scores table in the book using the WISC manual. Scan horizontally for your child's raw score. Locate the GAI composite score, accompanying percentile rank and confidence interval.
Write down the composite score, the percentile rank and the confidence interval (90% or 95%). This number will come in handy when you present your child for gifted or special education classes.