Question

You need to estimate the mean number of travel days per year for outside salespeople. The mean of a small pilot study was 160 days, with a standard deviation of 19 days. If you must estimate the population mean within 2 days, how many outside salespeople should you sample? Use the 98% 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 =   =19

Margin of error = E = 2

At 98% confidence level the z is ,

= 1 - 98% = 1 - 0.98 = 0.02

/ 2 = 0.02/ 2 = 0.01

Z/2 = Z0.01 = 2.326 ( Using z table    )

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

n = ( 2.326*19 / 2 )2

n =488.2777

Sample size = n =488