A test consists of 10 multiple choice questions, each with 5 possible answers, only one of which is correct. Find the mean and the standard deviation of the number of correct answers.

Question

anonymous · Answer

So, 50 possible answers total, 10 of which are correct?

anonymous · Answer

Yes.

anonymous · Answer

I'm not sure I understand the question. Is it assuming random guessing on all the questions, and wants the mean = expected value?

anonymous · Answer

I think it's asking you the mean if the person gets a 100, I'm not sure, and yes, mean is expected value. I know the answer. 

Mean=2
Standard Deviation= 1.26

My professor wants me to show her how she got the answer.

anonymous · Answer

The expected value part is easy. If there are 5 choices, the the chance of getting one correct is 1/5 or 20%. 20% of ten questions is 2 correct answers. For standard deviation. You'll have to research that a little 'cause I don't remember at the moment. Try: http://stattrek.com/random-variable/mean-variance.aspx?Tutorial=AP