SO nervous - Information Systems test

[canyontothesky]

Don't know if anyone will respond to this, but I paid for Peterson's three practice tests on this subject. I still have 3 more nights before the test, but I took two practices so far and on the first I got 81%, and on the second (which was much, much harder) I got a 51%. What's up with that? I used this practice book for the Management CLEP to convert raw score to actual score, and both times were passing scores (I think you need around 43% raw to fail, is that true? something less than 50%, it looked like). So with some more studying, you think I'll be ok? Can't fail it this time.