When I took engineering calc. at a major university. There was approximately 500 people in the class taught in a large lecture hall. The first test comes and panic sets in, the professor posts the results in a bell curve on the projector. The average test grade was around 27% out of a 100. About 10 people scored in the high 90's and about another 30 more passed above 70. The rest surprising where all in the curve between 23 to 33%. The prof. told the class he would weight the grade by about 50 points and the majority passed.

5 years later at a grad party with my wife, chatting up a engineering/math TA and asked him about how come the curve was so big & the tests were so damn hard. He flat out told me the tests had no bearing on whether you passed unless you scored in the 90's. The math/engineering department just wanted you to turn in the weekly homework packs that took about 25 to 30 hours a week to complete. These were graded pass/fail and determined whether you actually passed the class.