Many news outlets, including my local paper, recently carried an AP story about a report issued by The Education Trust.  In the report, we learn that one out of every four people who take the U.S. military’s entrance exam fail.  The report and article use these findings to indict the education system in the United States.  Unfortunately, it is more of an indictment of the authors.  While the Armed Services Vocational Aptitude Battery (ASVAB) is required at “hundreds” of high schools, it is by no means ubiquitous.  The sample, then, is not random, but largely self-selecting.  Consider also that the ASVAB is not required for officer-track students (i.e. service academies and ROTC), but only for enlisted personnel.  When I first read the article, I immediately realized that the conclusion wasn’t justified.

It wasn’t until I did some further research that I realized exactly how wrong the authors were.  As it turns out, ASVAB scores are given as percentiles.  In other words, to get into the Army, you need not get 31% of the questions correct, you need to score better than 31% of the other test takers.  This means that the military automatically rejects the lowest scores, no matter how good or bad they may be on an absolute scale.  The military grants waivers for low scores in certain situations, which is why only a quarter of test takers fail.

So the news here is that 25% of students fail an exam designed for them to fail.  In other news, water is wet.  On second thought, maybe this is an indictment of the education system, but not in the way suggested.  An elementary understanding of statistics immediately calls into question the credibility of the study.  One paragraph of a Wikipedia article ruins the starting point of the article.  The education system may have flaws, but the only flaws exposed by this article are the lack of statistical understanding and simple research ability possessed by The Education Trust and AP writers Christine Armario and Dorie Turner.