The score students receive on their exams and homework assignments are combined using a formula that is announced in the beginning of the course. The result is the student's "raw" score. Raw scores are then mapped into letter grades. This mapping is "relative" rather than "absolute". That is, it is based on the distribution of the raw scores in the specific class being graded. So the same raw score may be mapped into different letter grades in different semesters.
The following grades were assigned by this instructor in his years at GMU. These numbers are for undergraduate upper level courses only (i.e., 300-400 level), and include only students who completed the course (i.e., other than W, S/A, N/A, AU, IN, etc.):
The average grade is approximately 2.5 (between B and C).
Remember: this average accumulated over a long period. It does not mean that a specific class will obey these numbers exactly.