An insurance company is trying to estimate the average number of sick days that full-time food service workers use per year. A pilot study found the standard deviation to be 2.5 days. How large a sample must be selected if the company wants to be 95% confident of getting an interval that contains the true mean with a maximum error of 1 day?
Additional Information
This kinds of problem is a part of Statistics and it is about estimating the average number of sick days that a full time food service workers take per year. For this study, an approximate size of the sample needs to be decided.