A research company desires to know the mean consumption of m

A research company desires to know the mean consumption of milk per week among people over age 20. They believe that the milk consumption has a mean of 4.5 liters, and want to construct a 99% confidence interval with a maximum error of 0.09 liters. Assuming a standard deviation of 1.2 liters, what is the minimum number of people over age 20 they must include in their sample?

Solution

1 - 0.99 = 0.01

Z= 2.57

n = [(2.57*1.2) / 0.09 ]^2

n = 1174.20