The ASVAB test is broken down into nine smaller tests: Paragraph Comprehension, Word Knowledge, Arithmetic Reasoning, Mathematics Knowledge, Mechanical Comprehension, Shop Information, Automotive Information, Electronics Information and General Science.
Each test has its own set of questions and time limits, with increasingly more difficult questions closer to the end of each test and correspondingly larger values for later questions.
The first and most important set of scores is known as the Armed Forces Qualification Test, or AFQT, score.
The Paragraph Comprehension and Word Knowledge test scores are individually multiplied by two and then added to the scores of the Arithmetic Reasoning and Mathematics Knowledge tests to create what is known as the AFQT Raw Score.
The raw score is then calculated in a five tier percentile system ranging from 0-99. Most jobs in the military are only available to those scoring in the top tier, a 93rd percentile or higher. Those finishing in the lowest tier, the 9th percentile or lower, are prohibited from enlisting in the military, and those in the fourth tier, which ranges from the 30th to the 10th percentile, are very unlikely to be accepted.
The other five tests are used in conjunction one or more of the first four tests to determine a recruit's ability to engage in a particular category of Military Occupational Specialties, or MOS. The Air Force uses AFQT scores to determine whether a recruit is qualified for a particular group of MOSes. The Navy uses Navy Enlisted Classifications or NECs in the place of an MOS although the two serve the same purpose.
The Coast Guard has the highest AFQT standards, with a minimum allowable score of a 40, with the majority of enlistees requiring a score in the 60s or higher.
The Army and Marines have the lowest standards, requiring a score in the low 30s and a score above 50 for those with a General Equivalency Diploma or GED in the place of a High School diploma. The Navy and Air Force have requirements in the mid to upper 30s with the Air Force requiring a 65 as a minimum for GED recruits.
Poor AFQT scores can also be waived to an extent when an enlistee has an undergraduate or graduate college degree. On the opposite side of the spectrum, the chances of someone enlisting without a high school diploma or an equivalent such as a GED are nearly unheard of and usually impossible in most branches of the military.