All military recruits must take the Armed Services Vocational Aptitude Battery (ASVAB) to qualify for enlistment. The ASVAB is
essentially an IQ test (correlation = 0.8). The ASVAB predicts SAT scores (correlation = .82). And it
correlates with ACT scores (0.77).
To qualify, recruits must score higher than roughly one-third of all who take the ASVAB. The lowest acceptable percentile score to join is 36 for the Air Force, 35 for the Navy, 32 for the Marine Corps, and 31 for the Army.
By definition, the worst test taker who makes it into the military still scores higher than one-third of his or her peers. The military intentionally slices off the bottom third of test-takers, not allowing them to join.
Moral quandaries aside, this means that the military selects for the upper two-thirds of ASVAB test takers.
Another study found that among those who finish high school, about 1 in 4 (23%) people do not attain the minimum ASVAB score to join any branch of the military.