Evaluating course difficulty

[toastman]

When certain schools say they take into consideration the difficulty of courses you take, how do they evaluate its difficulty? Do they do it by class average, or subject matter, etc? One thing I've noticed is that my science courses typically have a class average of high 70s to low-mid 80s. Whereas my "bird" electives typically have an average of low 70s.

[NutritionRunner]

Not all universities include the class average on their transcripts, so how would medical schools be able to evaluate the difficulty in that fashion?

I would assume (although I may be wrong) that they look at the level of the course (ie. first, second, third, fourth, etc.) and what a typical course load is for your program. For example, in engineering we had a couple of semesters where we had to take 6 full courses per semester (instead of the 'regular' 5 for standard arts and science programs), so I assume schools that look at program/course difficulty would take that into account. They might also look at the credit weight of the course. But I honestly don't know how they evaluate difficulty!