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2. A research team compared two methods of measuring treadwear on tires. Eleven tires were each measured for treadwear by two different methods: one method was based on weight while the other method was based on groove wear. For convenience, each tire was measured first by weight method and then second by the groove wear.

a. The two samples are which of the following: two independent or two dependent (matched pairs)? Explain. The two samples used are independent samples. The tires were measured for weight and then by groove. The weight of the tire may be affected by the amount of groove wear on the tire.
b. What type of study is found—observational or randomized experiment? Explain. This study is a randomized experiment. The measurements are randomly assigned to the tire.
c. What is the experimental unit? The experimental unit is the tire.
d. What is the response variable? The response variable is the treadwear.
e. What is the explanatory variable? The explanatory variable is the measurements (weight or groove wear).