Here's the link to the technical report Jennie mentioned:



To calculate the GAI you need to know the General Ability Sum of Scaled Scores.

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The General Ability Sum of Scaled Scores is the sum of scaled scores for three Verbal Comprehension subtests (i.e., Vocabulary, Comprehension, and Similarities) and three Perceptual Reasoning subtests (i.e., Block Design, Matrix Reasoning, and Picture Concepts)...

Locate the General Ability Sum of Scaled Scores in the extreme left column of Table 1. Read across the row to determine the GAI composite score.