A survey is planned to determine the mean annual family medical expenses of employees of a large company. The management of the company wishes to be 90% confident that the sample mean is correct to within + $60 of the population mean annual family medical expenses. A previous study indicates that the standard deviation is approximately $319. a. How large a sample is necessary? b. If management wants to be correct to within +$15, how many employees need to be selected? Click here to view page 1 of the cumulative standardized normal distribution table. Click here to view page 2 of the cumulative standardized normal distribution table. a. How large a sample is necessary? n= (Round up to the nearest integer.)

You want to know the percentage of utility companies that earned revenue greater than 94 million dollars. If the mean revenue was 60 million dollars and the data has a standard deviation of 15 million, find the percentage. Assume that the distribution is normal. Round your answer to the nearest hundredth.

An engineer wishes to determine the width of a particular Electronic Component. If she knows that the standard deviation is 3.8 mm how many of these components should she consider to be 90% sure that mean will be 0.2 mm

This is math economics