Question 80420
a nurse at a local hospital is estimating the weight of infants. how large a sample must she select if she desires to be 95% confident that the true mean is within 3 ounces of the sample mean? sd=7
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E = z*sigma/sqrt(n)
sqrt(n) = z*sigma/E
Your Problem:
sqrt(n) = 1.96*7/3
sqrt(n) = 4.57333
n= 20.91..
Rounding up: n=21
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Cheers,
Stan H.