The purpose of this quantitative study was to examine the ability of standardized test scores to predict the performance of students in first-year mathematics courses, and the extent to which these tests displayed differential validity among various subgroups. Using discriminant analysis, it was established that the following percentages of students were correctly classified into passing and not passing groups, using the listed independent variables: 1) SAT mathematics scores - 58.6%, 2) SAT verbal scores - 50.6%, 3) ACT mathematics scores - 54.7%, and 4) ACT verbal scores - 56.3%. New predictive models were created using standardized test scores in combination with students high school GPA, and high school rank to increase correct classification into passing and not passing groups to 67.1% using the SAT, 67.4% using the ACT, and 68.5% using a combination of the SAT and ACT. Using three-way ANOVA, it was determined that there was a significant three-way interaction between gender, ethnicity, and socioeconomic status (income), and a significant two-way interaction between gender and socioeconomic status (income) for both the SAT and ACT. An analysis of main effects determined that ethnicity and socioeconomic status (income) displayed statistically significant differences in the mean scores of students on the SAT and ACT. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]