Question

bicycles have three types of tires: mountain bike, road touring, and cruising. an experiment is to be conducted to determine whether the mileage before a tire change is needed is the same for all three types of tires. in previous studies, it was determined that bicycle weight (light, normal, heavy) is associated with frequency of tire changes, but bike type (mountain, road, cruising) is not associated with frequency of tire change. how would blocking best be used?
by blocking on bicycle type
by blocking on mileage
blocking is not suggested
by blocking on tire type
by blocking on bicycle weight

Explanation:

Blocking is used to control for variables that affect the response (here, mileage before tire change) but are not the main focus of the experiment. Since bicycle weight is associated with the frequency of tire change (related to mileage), blocking on this variable will reduce experimental variability. Bicycle type is not linked to the response, so it is not a suitable blocking variable.

Answer:

By blocking on bicycle weight