SOLUTION: A test consists of 90 multiple choice questions, each with five possible answers, only one of which is correct. Find the mean and the standard deviation of the number of correct an

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Question 463368: A test consists of 90 multiple choice questions, each with five possible answers, only one of which is correct. Find the mean and the standard deviation of the number of correct answers.
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
The experiment follows a binomial experiment with n = 90, p = 1/5, and q = 4/5.
==> mu+=+np+=+90%2A%281%2F5%29+=+18, and
sigma%5E2+=+npq+=+90%2A%281%2F5%29%2A%284%2F5%29+=+72%2F5
==> sigma+=+sqrt%2872%2F5%29+=+%286sqrt%2810%29%29%2F5