Some people believe that higher-octane fuels result in better gas mileage for their car. To test this claim, a researcher randomly selected 11 individuals to participate in the study. Each participant received 10 gallons of gas and drove his car on a closed course. The number of miles driven until the car ran out of gas was recorded. A coin flip was used to determine whether the car was filled up with 87-octane or 92-octane first, and the driver did not know which fuel was in the tank. Complete parts (a) through (e).

87_octane 

87_octane	235	257	244	214	114	286	314	230	192	203	548
92_octane	236	237	230	224	119	296	350	240	185	209	562

Paired T-Test and CI: 92 Octane, 87 Octane

Paired T for 92

Octaneminus−87

Octane

	N	Mean	StDev	SE Mean
92 Octane	1111	262.545262.545	115.038115.038	34.68534.685
87 Octane	1111	257.909257.909	109.354109.354	32.97132.971
Difference	1111	4.6364.636	15.04215.042	4.5354.535

(a) Why is it important that the matching be done by driver andcar?

A. It cuts the cost of doing the research.

B. It allows all of the trials to be done at the same time.

C. It allows each driver to determine which fuel is best for their car.

D. How someone drives and the car they drive result in different fuel consumption.

(b) Why is it important to conduct the study on a closed track?

A. So that the researcher can watch the drivers

B. So that each car uses the same amount of gas

C. So that each car travels the same distance

D. So that all drivers and cars have similar driving conditions

(c) The normal probability plots and linear correlation coefficients for miles on 87-octane and miles on 92-octane are given. The correlation between 87 octane and the expected z-scores is 0.876. The correlation between 92 octane and the expectedz-scores is 0.878. Are either of these variables normallydistributed?

A. No, neither variable is normally distributed.

B. Yes, 87-octane is normally distributed.

C. Yes, both variables are normally distributed.

D. Yes, 92-octane is normally distributed.