Their predictive value lies in that they are essentially intelligence tests. In the vast scheme of things (and I'm not talking about individual students here), higher scores equate with higher intelligence. Higher intelligence is correlated with success in college.
Not all of their predictive value results from their g-loading, although much of it does, according to a recent paper:
http://www.sciencedirect.com/science/article/pii/S0160289608000603SAT and ACT predict college GPA after removing g
Thomas R. Coyle and David R. Pillow
University of Texas at San Antonio, USA
Intelligence
Volume 36, Issue 6, November–December 2008, Pages 719–729
Abstract
This research examined whether the SAT and ACT would predict college grade point average (GPA) after removing g from the tests. SAT and ACT scores and freshman GPAs were obtained from a university sample (N = 161) and the 1997 National Longitudinal Study of Youth (N = 8984). Structural equation modeling was used to examine relationships among g, GPA, and the SAT and ACT. The g factor was estimated from commercial cognitive tests (e.g., Wonderlic and Wechsler Adult Intelligence Scale) and the computer-adaptive Armed Services Vocational Aptitude Battery. The unique variances of the SAT and ACT, obtained after removing g, were used to predict GPA. Results from both samples converged: While the SAT and ACT were highly g loaded, both tests generally predicted GPA after removing g. These results suggest that the SAT and ACT are strongly related to g, which is related to IQ and intelligence tests. They also suggest that the SAT and ACT predict GPA from non-g factors. Further research is needed to identify the non-g factors that contribute to the predictive validity of the SAT and ACT.
Keywords
g factor; SAT; ACT; Grade point average; GPA; Intelligence; IQ; Structural equation modeling; SEM; National Longitudinal Study of Youth; NLSY; Armed Services Vocational Aptitude Battery; ASVAB
