Question

You need to estimate the mean number of travel days per year for outside salespeople. The mean of a small pilot study was 150 days, with a standard deviation of 30 days. If you must estimate the population mean within 6 days, how many outside salespeople should you sample? Use the 98% confidence level.

Answer 1

Solution :

Z_$\alpha$/2 = Z_0.01 = 2.326  

sample size = n = [Z_$\alpha$/2* $\sigma$ / E] ²

n = [2.326 * 30 / 6]²

n = 135.26

Sample size = n = 136