An employee of an on-campus copy center wants to determine the mean number of copies before a

Question:

An employee of an on-campus copy center wants to determine the mean number of copies before a cartridge needs to be replaced. She records the life length in thousands of copies for 43 cartridges and obtains
n = 43 = 8.12 s = 1.78 thousand copies
Obtain a 90% confidence interval for the population mean, μ, number of copies in thousands before a cartridge should be replaced.