Protecting marathon runners. An ultramarathon, as you might guess, is a running longer than 26.2 miles of a marathon. Ru

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Protecting marathon runners. An ultramarathon, as you might
guess, is a running longer than 26.2 miles of a marathon. Runners
commonly develop respiratory infections after an ultra-bully. Take
600 milligrams of vitamin C daily will reduce these infections? The
researchers assigned runners randomly to receive vitamin C or a
placebo. Separately, they also randomly assigned these treatments
in a group of non-runners the same age as the runners. All subjects
were observed for 14 days after the big race to see if infections
developed.
a) What is the name of this experimental design?
b) Use a diagram to outline the design.