Whereas recruits who join as officers tend to be upwardly-mobile,[14][15] most enlisted personnel have a childhood background of relative socio-economic deprivation.[16][17][18] For example, after the US suspended conscription in 1973, "the military disproportionately attracted African American men, men from lower-status socioeconomic backgrounds, men who had been in nonacademic high school programs, and men whose high school grades tended to be low".[14]
First, the ASVAB measures your accumulated knowledge in different areas. So if you are currently in school, stay focused and study hard. Your overall knowledge gained in school will most likely be reflected in your ASVAB score. Second, though accumulated knowledge is important, you may be able to raise your score by preparing specifically for the ASVAB, especially in areas where you are weak. Various study guides are available for this purpose (listed left).
My recruiter told me about this book so I ordered it and got it 3 days later from the Military Bookstore. I got this book and it is awesome. The cd works great and every thing I needed and more to help me was in there. I recommend this book to everyone who is thinking of going in the service and wants to get a real job! GET THIS BOOK AND SCORE HIGH!!!!”
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.
To coordinate military strategy with political affairs, the President has a National Security Council headed by the National Security Advisor. The collective body has only advisory power to the President, but several of the members who statutorily comprise the council (the Secretary of State, the Secretary of Energy and the Secretary of Defense) possess executive authority over their own departments.[18]

Focusing Your Study - As you take more and more sample tests you begin to get a feel for the topics that you know well and the areas that you are weak on.  Many students waste a lot of valuable study time by reviewing material that they are good at (often because it is easier or makes them feel better).  The most effective way to study is to concentrate on the areas that you need help on.
One ASVAB sub-measure, the Armed Forces Qualification Test (AFQT)--which is just a separate analysis of the same tests that focuses only on four of the subtests--is also population-referenced, but its score from 1-99 is a percentile score. This means that if you score a 73, you scored as well as or higher than 73% of test-takers in the national sample.