The Air Zoom series is one of Nike s most expensive line of race-running shoes

The Air Zoom series is one of Nike s most expensive line of race-running shoes. A statistician is curious if Nike s most expensive line does significantly improve running time when compared to their less expensive race-running shoes, the Zoom Victory series. The statistician will conduct an experiment using the randomized block design. The blocks will be classification of the runner as recreational or professional. He will randomly select 75 runners for each classification, then randomly assign which individuals in each block will receive the Air Zoom running shoe or the Zoom Victory running shoe. Participants will be asked to run one-mile, their times will be recorded.

Part (a) What is a statistical advantage of blocking by recreational and professional?

Part (b) How would it be confounding if the statistician allowed runners to choose between the Air Zoom and the Zoom Victory shoe instead of randomly assigning them?

Part (c) Explain how the design of the experiment will address replication. What is the benefit of the replication?