A librarian wants to estimate the average number of book a patron will check out over a years time. She believes from past studies the standard deviation is 20 books per year. If she samples 100...

A librarian wants to estimate the average number of book a patron will check
out over a years time. She believes from past studies the standard deviation is
20 books per year. If she samples 100 patrons, with what probability can she
assert than the error in her estimate will be less than 5 books per year? (