Standard Deviation Help Please

green.tee

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Nov 4, 2010
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A new drug has been found to be effective in treating 73% of the people afflicted by a certain disease. If the drug is administered to 491 people who have the disease, what are the mean and the standard deviation of the number of people for whom the drug can be expected to be effective? (Round your answers to two decimal places.)
358.43 (mean) I have calculated the mean, but I am stuck on standard deviation :(
 
Just as the mean is \(\displaystyle np\), the standard deviation is \(\displaystyle \sqrt{np(1-p)}\)
 
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