Students are unprepared for a multiple choice quiz with 25 questions. Each question has 5 possible answers.
Let, out of 5 possible answers only one is correct.
Hence, mean=n*p=25*0.20=5 (n=no. of questions and p=proportion of correct answers)
Standard deviation=`sqrt(n*p*(1-p))` where n=no. of questions and p=proportion of correct answers
Here, n=25,p=0.20. Now putting the values we get:
Therefore, mean=5, standard deviation=2.