Chamberlain focuses on english, math, and vocabulary. They take an average of your scores to get your total score which has to be above 75%. They do look at your science scores though (not for your average).
A few years ago I took the same test at my community college and made an 85% without studying a bit (i didnt know about the study guide). When I took the test at Chamberlain last Friday, I made exactly a 75%. I studied for a day or so, I am retaking it this Friday just to bring up my scores. This time I have been studying since Monday.
If you are studying hard I don't think you will have a problem. Oh, and by the way, whic campus are you going to? I am going to Houston