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- Thread starter micmom3
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What are the z-values of the difference?micmom3 said:an insurance co. is trying to to estimate the number of sick days that workers take per year. a pervious study indicated that the standard deviation was 2.8days. how large of a sample must be selected if the company want to be 95% confident that the true mean differs from the sample mean by no more than 1 day

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Are you saying that you need lessons on z-scores, etc?micmom3 said:explain

Please be specific. Thank you!

Eliz.

There is a simple formula for this kind of sample size problem. It should be in your textbook, possibly in the chapter that talks about confidence intervals for a normal mean with known standard deviation.micmom3 said:

Thanks