Question

You need to estimate the mean number of travel days per year for outside salespeople. The mean of a small pilot study was 140 days, with a standard deviation of 15 days. If you must estimate the population mean within 3 days, how many outside salespeople should you sample? Use the 99% confidence level. (Round the intermediate calculation to 3 decimal places. Round the final answer to the nearest whole number.)                                   

Number of outside salespeople           

Answer 1

Solution :

Given that,

standard deviation =s =   =15

Margin of error = E =3

At 99% confidence level the z is,

= 1 - 99%

= 1 - 0.99 = 0.01

/2 = 0.005

Z/2 = 2.576

sample size = n = [Z/2* / E] 2

n = ( 2.576* 15/ 3)2

n =165.89=166 rounded