Question

You wish to estimate the mean number of travel days per year for salespeople. The mean of a small pilot study was 150 days, with a standard deviation of 42 days.

If you want to estimate the population mean within 6 days, how many salespeople should you sample? Use the 99% confidence level. (Use z Distribution Table.) (Round up your answer to the next whole number.)

Answer 1

Solution :

Given that,

standard deviation =  σ =42

Margin of error = E = 6

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 *  σ/ E]2

n = ( 2.576*42 /6 )2

n =325.15

Sample size = n =326