I will be taking the Natural Sciences CLEP in 2 weeks.

I've read the specific feedback on this exam, but after just taking a Peterson's prep exam, I'm a little unnerved!

I have been studying the following:
1) REA subject exam (Natural Sciences)
2) Instant Cert (biology)
3) Biology textbook
4) REA Biology (made 60 on REA biology practice test)

I am doing fairly well on the end of chapter exams and feel like I have a pretty good grasp of the material, but taking the Peterson's exam was like reading a foreign language! Does anyone know how this exam stacks up against the real exam? Also, do I go by the "score" listed or the percentile Peterson's gives me to judge my performance against an actual CLEP score? Or is there no basis for comparison?

Thanks!