1. An experiment was performed to determine if a new gasoline additive can increase the gas mileage of cars. In the experiment, six cars are selected and driven with and without the additive. The gas mileages (in miles per gallon, mpg) are given below.

Car Mpg w/additive Mpg w/o additive

1 24.6 23.8

2 18.9 17.7

3 27.3 26.6

4 25.2 25.1

5 22.0 21.6

6 30.9 29.6

a. Using R or SAS Examine the summary statistics, histogram, and the 95% mean confidence interval of the differences in mpg with and without additive.

b. Is there evidence that additive improves mpg?