The manager of a newly opened book store wants to estimate the average expenditure of his customers using a confidence interval. He estimates that the population standard deviation is approximately $20.00.

a) For a 99% confidence level, find the appropriate sample size necessary to achieve a margin of error of 4.00.

determine za/2=

The required sample sizen is

b.)For a 95% confidence level, find the appropriate sample size necessary to achieve a margin of error of 4.00.

Determine z a/2=

The required sample sizen is