The CAT-ASVAB is an adaptive test which means the test adapts to the ability of the test-taker. It is possible to administer a shorter test this way than with the pencil and paper test. When you complete a subsection of the test, you can then move onto the next section of the test without having to wait for an administrator. Subsections are still timed however and on average it takes about 1 ½ hours to complete the computer ASVAB.
Don’t be fooled by the appearance of the low numbers, the algorithm that computes the AFQT is very sophisticated. Just because your ASVAB score is 40 doesn’t mean that you only got 40% of the questions correct, it could simply mean that you lack strength in one area, but succeed with high praise in another. Your ASVAB score is only a means by which you are categorized for available positions; it is by no means a measure of intelligence.

Students are given a Standard Score for each of the subtests. Standard Scores are derived from your Raw Scores (total number of points you receive on each subtest). The Standard Scores are a statistically derived score that typically ranges from 30 and 70 for each subtest. The Standard Scores are created such that a 50 represents a mean (average) score and there is a standard deviation of 10 (implying that 95% of test takers are within two standard deviations, 20 pts, of the mean of 50).

After adding so much information to the aptitude test, there was a bit of difficulty interpreting the test results. In addition to that, a vast majority of test takers were deemed as being under qualified based on their test results. This is why the percentile change was made. It ensured that a 50% actually correlated with a person doing better than 50% of the test takers. Those revisions have worked hand-in-hand with the preparation of the armed forces.