Question: Suppose a department store wants to estimate the mean age of the customers who shop in a contemporary apparel department correct to within 3 years with 95% confidence. An estimate of the standard deviation is 12.5.

a) Approximately how large a sample would be required?

b) Suppose they wanted to be within only 1 year of the true mean with 98% confidence. Now how large a sample would be needed.

c) Find how large a sample would be needed if the level of confidence is changed to 99% and the bound to within 0.5 years.

d) What restricts companies from using as large a sample as they would like?