The military uses the verbal expression (VE) score to measure your communicative ability. The score goes toward computing the AFQT score as well as many of the military’s line scores. The military brass determine your VE score by first adding the value of your Word Knowledge (WK) raw score to your Paragraph Comprehension (PC) raw score. The result is then converted to a scaled score ranging from 20 to 62.
If you didn't earn a score that was high enough to be accepted to your chosen branch of the military, or if you didn't earn a line score high enough to qualify for a desired career option, then you may retake the ASVAB. You must wait a full month before you can take the ASVAB a second time. If you wish to take the test a third time, you must wait another month from the date of your second attempt. After the third attempt, there is a waiting period of 6 months before you can take the test again.
The ASVAB currently contains 9 sections (except the written test, which contains 8 sections). The duration of each test varies from as low as ten minutes up to 36 minutes for Arithmetic Reasoning; the entire ASVAB is three hours long. The test is typically administered in a computerized format at Military Entrance Processing Stations, known as MEPS, or at a satellite location called a Military Entrance Test (MET) site. The ASVAB is administered by computer at the MEPS, while a written version is given at most MET sites. Testing procedures vary depending on the mode of administration.[3]

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.
The Mechanical Comprehension section of the ASVAB practice test measures your understanding of basic mechanical principles and mechanisms. You may be asked why an intake valve on a pump opens when the piston goes down, or what direction friction is going when shown a diagram of a skier. The CAT-ASVAB has 16 questions in 20 minutes; the paper-and-pencil version has 25 questions in 19 minutes.
[1] See two documents: Sims, W.H. and Truss, A.R., A Reexamination of the Normalization of Armed Services Vocational Aptitude Battery (ASVAB) Forms 6, 7, 6E, and 7E (Alexandria, VA: Center for Naval Analyses, September 1980); and Laurence, J.H. and Ramsberger, P.F., Low-Aptitude Men in the Military: Who Profits, Who Pays? (New York: Praeger, 1991).  
The Student ASVAB is the most flexible of the exams. It is typically provided to high school students to help them assess their skills, job prospects, potential military positions, or college majors. The ASVAB for students is essentially the same as the MET ASVAB exam, only students are not necessarily testing for positions within the military. The students’ school counselors examine their scores and help them decide on what to do after graduating from high school. This test is still an important component of a student’s education because it can help them identify their strengths and weaknesses and help set them on the right track for their future career goals.