The occurrence of adverse impact is often determined using the Four-Fifths Rule:
“A selection rate for any race, sex, or ethnic group which is less than four-fifths (or eighty percent) of the rate for the group with the highest rate will generally be regarded by the Federal enforcement agencies as evidence of adverse impact.”
— Code of Federal Regulations Pertaining to the U.S. Department of Labor
Applications of the Four-Fifths Rule to examinees that qualify for entry into the military (i.e., those generally scoring in AFQT category IIIB or higher) and to examinees that qualify for enlistment incentives (i.e., those generally scoring in AFQT category IIIA or higher) suggest some adverse impact is associated with the ASVAB. Specifically, the qualification rates for African-American/Black applicants are less than four-fifths of the qualification rates for Caucasian/White applicants, for both entry into the military and enlistment incentives. Likewise, the qualification rates for Hispanic applicants are less than four-fifths of the qualification rates for Non-Hispanic White applicants, for both entry into the military and enlistment incentives.
Although adverse impact does occur on the ASVAB, the magnitude of Male/Female, White/Black, and Non-Hispanic White/Hispanic score differences on the Mathematical Knowledge, Arithmetic Reasoning, Word Knowledge, Paragraph Comprehension, and General Science subtests are similar to the magnitude of score differences between like groups on tests of similar domains in other high-stakes test batteries. The consistency of trends in effect sizes observed across different test batteries suggests that the adverse impact associated with the ASVAB reflects a societal phenomenon, rather than bias in the test.
This conclusion is supported by a study of the sensitivity and fairness of the ASVAB technical tests (Wise, Welsh, Grafton, Foley, Earles, Sawin, & Divgi, 1992). The study compared prediction of final school grades for Air Force and Navy technical training courses and scores on the Skill Qualification Test for first-term Army recruits. Data from large samples of males, females, whites, and blacks were analyzed, and the prediction lines were similar for all groups.