SOLUTION: If 9% of all calculators are defective, find the mean, variance and standard deviation of a lot of 500 calculators.

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Question 393634: If 9% of all calculators are defective, find the mean, variance and standard deviation of a lot of 500 calculators.
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
Let X = r.v. representing the # of defects.
Then mean is mu+=+E%28X%29+=+np+=+500%2A0.09++=45, variance is
sigma%5E2+=+npq+=+500%2A0.09%2A0.91++=40.95, and standard deviation is
sigma+=+sqrt%2840.95%29+=+%283sqrt%28455%29%29%2F10++=6.4 to the nearest tenth.