To compare four brands of tires, one of each brand was randomly assigned to the four tire locations on each of 50 cars. These tires were specially manufactured without any labels identifying the brand. After the tires had been on the cars for 30,000 miles, the researchers removed them and measured the remaining tread. They were not told which brand was which until the experiment was over.
a. What was the explanatory variable in this experiment?
b. What was the response variable in this experiment?
c. Was this experiment single-blind, double-blind, or neither? Explain.
d. Did this experiment use matched pairs, blocks, or neither? Explain.