A state job service employee wishes to estimate the mean number of people who register with the service each week.

A state job service employee wishes to estimate the mean number of people who register with the service each week. How many weeks should be sampled in order to estimate µ, the mean number of weekly registrants? The employee would like the margin of error to be less than 0.5 with probability of 0.95. Past records show the weekly standard deviation to be 2.5.