سؤال في الاحصاء

[وردي أحمر]

a student takes a 7 question multiple choice quiz with 4 choices for each question. if the student guesses at random on each question,answer the following

what is the standard deviation of the correct answer*
what is the mean number of incorrect answers*
if the lowest grade to get an a in the quiz is 6 correct out of 7,what is the probability of getting a in this q