Question

Suppose you are interested in determining the amount of time in minutes that commuters travel to school. You would like to use a 95% confidence that your sample mean is within 1.5 minutes of the true population mean. If the commute times have a standard deviation of 10 minutes, how many students should you include in your sample?

Answer 1

Solution

standard deviation =s =   =10

Margin of error = E =1.5

At 95% confidence level the z is ,

= 1 - 95% = 1 - 0.95 = 0.05

/ 2 = 0.05 / 2 = 0.025

Z/2 = Z0.025 = 1.96

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

n = ( 1.96*10 / 1.5 )2

n =170.74

Sample size = n =171