I understand Mean (Expected Value) and Variance of Random variables as outlined on this page. I can't seem to apply those concepts to this problem, however.
Say there's a class of 50 people answering a question. There is a 60% chance that any given student knows the answer. Let $X$ be the number of students who get the correct answer.
My general sense for Expected Value in this case is just $0.6 \cdot 50=30$. But I don't think that's correct.
I don't even know how to approach Variance in this case. Each student is equally likely to get the correct answer and I keep getting large numbers which make no sense:
That is obviously incorrect... can anybody offer any pointers?