8.17. Fuel Economy A company develops a new ethanol that is an alternative to 93 octane unleaded fuel. In an effort to evaluate the gas mileage associated with this new ethanol the company recruits 50 drivers in Grand Rapids, Michigan for a two-week study. Cars are randomly assigned to receive ethanol in the car's gas tank in one of the two weeks; in the other week a comparable brand of 93 octane unleaded fuel is put in the car's gas tank. At the end of each week the fuel economy of each car (in miles per gallon) is recorded.

(a) What is the response variable?

(b) What are the observational units?

(c) Is this independent data or dependent data?

(d) Explain your answer to part (c) in a sentence or two.

(e) Name a couple potential lurking variables that are accounted for by the study design. (See Section 2.6 for a review of lurking variables.)

(f) Name a couple potential lurking variables that are not accounted for by the study design. (See Section 2.6 for a review of lurking variables.)