several students take a multiple choice test with 10 questions. Each question has 5 possible answers, only 1 is correct. Find the mean and standard deviation for the number for correct answers for such students. I have n=10 but what is p and x?

You choose what is p and what is X.

It goes as follows.

Let X be the number of correct answers and p be the probability that a correct answer is obtained.

Therefore,

X ~ B(10, 0.2)

Why 0.2? It's because you have 1 correct answer out of 5 choices, hence, we have a chance of 1 in 5 to get a correct answer or 1/5 = 0.2.

We have to assume though that the students pick the answers randomly.

Can you find the mean and standard deviation now? Post what you get! :)