The IRT model underlying ASVAB scoring is the three-parameter logistic (3PL) model. The 3PL model represents the probability that an examinee at a given level of ability will respond correctly to an individual item with given characteristics. Specifically, the item characteristics represented in the 3PL model are difficulty, discrimination (i.e., how well the item discriminates among examinees of differing levels of ability), and guessing (i.e., the likelihood that a very low ability examinee would respond correctly simply by guessing).
During the war, significant advances were made in military communications through increased use of radio, military intelligence through use of the radar, and in military medicine through use of penicillin, while in the air, the guided missile, jet aircraft, and helicopters were seen for the first time. Perhaps the most infamous of all military technologies was the creation of the atomic bomb, although the exact effects of its radiation were unknown until the early 1950s. Far greater use of military vehicles had finally eliminated the cavalry from the military force structure.

The percentages of FY 1999 active duty NPS accessions in each AFQT category are shown in Table 2.8. The percentage of recruits in Categories I and II was approximately the same as their civilian counterparts (males - 39 versus 39 percent; females - 34 versus 33 percent). Category III accessions greatly exceeded civilian proportions (males - 61 versus 30 percent; females - 66 versus 37 percent), while the percentage of recruits in Category IV was much lower than in the civilian population (males - 1 percent versus 20 percent; females - less than 1 percent versus 22 percent). The low percentage of Category IV recruits is, in part, a result of DoD limits of 4 percent Category IV recruits, with even lower Service limits. Ten percent of civilian males and 9 percent of civilian females scored in Category V; DoD allows no Category V recruits.

Understanding the ASVAB score range is to understand standard deviations. The highest score on the ASVAB is a 99 and the lowest score is a one. Scores are based on the mean of all examinees. This is to say that a score of 50 would account for an average score. Each increment of 10 represents a single standard deviation from the mean score. So, for example, a score of 80 would be three standard deviations better than the meanwhile a score of 30 would be two standard deviations lower than the mean score.
Under the Student Loan Repayment Program, when you enlist the Army will pay back up to $65,000 in qualified education loans (up to $20,000 for reservists), the Navy up to $65,000 and the Air Force up to $10,000. Each year 15% of the loan balance or $500, whichever is greater, will be repaid by SLRP. There may also be annual and cumulative caps on the amount repaid. Participants must score 50 or higher on the Armed Forces Qualifications Test (AFQT). SLRP must be requested at the time of enlistment or reenlistment. Qualified education loans include federal education loans such as the Perkins, Stafford, PLUS, or Consolidation loans, but not private alternative loans. Defaulted loans are not eligible. Payments made under the SLRP are considered taxable income.
There is another ASVAB score that's equally important, if not more so, because it is the score that determines if a person is eligible for military service. It's the Armed Forces Qualification Test score, or AFQT score. This score is calculated from only four of the nine Standard Scores on the ASVAB - Arithmetic Reasoning (AR), Mathematics Knowledge (MK), Paragraph Comprehension (PC), and Word Knowledge (WK). First, the WK and PC scores are added together, then the sum is doubled. This is known as the Verbal Expression (VE) score. The VE, MK, and AR scores are then added together, and the sum is the AFQT. This score is a straight percentile measure, expressed as a number from 1-99. The number is the percentage of people who scored lower than the test taker. For example, if a person receives an AFQT score of 63, that means that he did better on the test than 63% of the people who have taken it.
The Armed Forces Qualification Test (AFQT) is used by all of the Services to determine if an applicant is eligible for the military. Four of the ASVAB subtests are combined to form the AFQT. It measures general cognitive ability and is composed of verbal and mathematics subtests. AFQT scores are grouped into categories for reporting purposes. The table below shows the AFQT categories and the percentile score ranges corresponding to the categories. Applicants that score in AFQT category IIIA or higher may qualify for enlistment incentives.