<PRE><B>Question 363493</B>
A researcher is interested in estimating the noise levels in decibels at area urban hospitals. She wants to be 98% confident that her estimate is correct. If the standard deviation is 4.74, how large a sample is needed to get the desired information to be accurate within 0.69 decibels? Show all work.
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Since E = zs/sqrt(n)
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n = [zs/E]^2
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n = [2.3263*4.74/0.69]^2 = 256 when rounded up
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Cheers,
Stan H.</PRE>