A researcher wants to determine if two different autotype obtain significant difference in gas mileages. The dependent variable is the number of miles per gallon (mpg) for Car X and Car Y while the independent variable is the auto type. The experiment will use 12 Car X and 12 Car Y automobiles, each driven over identical courses for 350 miles. Assume normal distribution. Use 0.05 level of significance.

Car X Car Y (mileage) 34.50 38.50 36.20 39.20 33.20 33.20 37.00 39.00 32.70 36.70 33.10 35.10 30.50 38.70 37.20 36.30 33.50 33.50 32.00 34.90 36.20 36.80 35.70 37.70