SOLUTION: . Several students are unprepared for a multiple-choice quiz with 20 questions, and all of their answere are guesses. Each question has 4 possible answers, and only one of them is
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Question 419120: . Several students are unprepared for a multiple-choice quiz with 20 questions, and all of their answere are guesses. Each question has 4 possible answers, and only one of them is correct.
A) Find the mean and standard deviation for the number of correct answers for such students.
B) Would it be unusual for a student to pass by guessing and getting at least 16 correct answers? Why or why not? Answer by ewatrrr(24785) (Show Source):
Hi
Several students are unprepared for a multiple-choice quiz with 20 questions,
and all of their answere are guesses. Each question has 4 possible answers,
and only one of them is correct. P(correct) = .25 and P(incorrect)= .75
A) mean = 20*.25 = 5 SD = sqrt(20*.25*.75) = 1.9365
B) P(at least 16 correct by guessing) is so small...highly unusual.
Note: The probability of x successes in n trials is:
P = nCx* where p and q are the probabilities of success and failure
respectively. In this case p = .25 and q = .75
nCx =
