Additionally, many ASVAB practice tests have a section explaining the answer choices. It can be tempting to read the explanation and think that you now have a good understanding of the concept. However, an explanation likely only covers part of the question’s broader context. Even if the explanation makes sense, go back and investigate every concept related to the question until you’re positive you have a thorough understanding.
AFQT scores are the primary measure of recruit potential. Figure 2.7 indicates the percentage of NPS recruits who scored at or above the 50th percentile (Categories I–IIIA) since FY 1973. Numerical data are in Appendix D, Table D-12. The drop in Category I–IIIA recruits after FY 1976 was due primarily to the miscalibration of the ASVAB.  In FY 1976, when new versions of the ASVAB were introduced, an error in calibrating the score scales made the new versions "easier" than the old versions (i.e., applicants received test scores higher than their actual ability). In FY 1980, an independent study of the calibration was made and the test was correctly calibrated. Then, Congress added legal provisions stipulating that no more than 20 percent of accessions could be in Category IV and that such accessions had to be high school diploma graduates.  However, as previously stated, Defense Planning Guidance decreases this limit even further, allowing no more than 4 percent of recruits to come from Category IV.
I just had to thank you guys for the test prep! I am a former Marine that decided to reenter the military and much to my surprise, I had to retake the AFQT!!! The last time I even looked at a math or English problem had to be at least 6 or seven years ago. I bought the guide as a last minute prep, I mean maybe 5 hours before the test. Like I said, I didn't even know I had to retake the test and had ZERO preparation! The job I wanted required a pretty high GT score and I was nervous about even passing the test let alone receiving the score I needed. I read the guide through only once before test time and needless to say, the only way I passed was thanks to your refresher!! Sgt. Brian