Posted by Valerie on Tuesday, November 2, 2010 at 9:02pm.
A researcher is interested in estimating the noise levels in decibels at area urban hospitals. She wants to be 90% confident that her estimate is correct. If the standard deviation is 4.13, how large a sample is needed to get the desired information to be accurate within 0.68 decibels?

statistics  MathGuru, Friday, November 5, 2010 at 7:42pm
Formula:
n = [(zvalue * sd)/E]^2
...where n = sample size, zvalue will be found using a ztable for 90% confidence, sd = 4.13, E = 0.68, ^2 means squared, and * means to multiply.
Plug the values into the formula and finish the calculation. Round your answer to the next highest whole number.
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