SOLUTION: Several students are unpreapred for a surprise true/false test with 9 questions and all of their answers are guesses. Find the mean and standard deviation for the number of correc
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Question 506626: Several students are unpreapred for a surprise true/false test with 9 questions and all of their answers are guesses. Find the mean and standard deviation for the number of correct answers. Would it be unusual for a student to p[ass by guessing and getting at least 4 correct answers?
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
Several students are unpreapred for a surprise true/false test with 9 questions and all of their answers are guesses. Find the mean and standard deviation for the number of correct answers. Would it be unusual for a student to pass by guessing and getting at least 4 correct answers?
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Binomial Problem with n = 9 and p = 1/2
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mean = np = 9*(1/2) = 4.5
std = sqrt(npq) = sqrt[2.25] = 1.5
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P(4<= x <=9) = 1-P(0<= x <=3) = 0.7461
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Cheers,
Stan H.
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