the average gas mileage for the new Honda Pilot If you want

the average gas mileage for the new Honda Pilot. If you want a 90% confidence interval with a maximum margin of error of 2.0, what sample size is necessary? Use a presample standard deviation of 9.8

Solution

Given a=1-0.9=0.1, Z(0.05) = 1.645 (from standard normal table)

So n=(Z*s/E)^2

=(1.645*9.8/2)^2

=64.97166

Take n=65