The GIA represents a distillate of several cognitive abilities. The Technical Manual for the WJ IV™ COG provides smoothed g weights for each of the seven tests that are included in the GIA score. The weights by technical age groups suggests that at any given age the Gf and Gc tests combined contribute to about 35% of the GIA score, whereas approximately 65% of the observed score is based on the other tests which comprise the GIA. As such, the calculation of the GIA score goes beyond simply averaging the tests which comprise the composite, and is based on weighting noted above. Because the GIA takes into consideration abilities in other domains aside from Gf and Gc, it can be influenced by how someone performs in those domains (e.g., working memory, long-term memory and retrieval, processing speed, etc).
Examiner's also have access to the Gf-Gc Composite, an additional Cognitive Composite, barring they've administered the appropriate tests to derive it. This composite is considered to be a special-purpose measure of intellectual ability based on four academically predictive tests that represent the two-highest order (g-loaded) CHC factors. When combined, Gf and Gc represent 100% of the contribution to the measurement of an individual's capacity which is defined by the Gf-Gc Composite. In summary, the Gf-Gc Composite does not consider performance within any other domains in its calculation, whereas, the GIA does.
