Vitamin C for marathon runners An ultramarathon, as you

Chapter , Problem R4.10

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Vitamin C for marathon runners An ultramarathon, as you might guess, is a footrace longer than the 26.2 miles of a marathon. Runners commonly develop respiratory infections after an ultramarathon. Will taking 600 milligrams of vitamin C daily reduce those infections? Researchers randomly assigned ultramarathon runners to receive either vitamin C or a placebo. Separately, they also randomly assigned these treatments to a group of nonrunners the same age as the runners. All subjects were watched for 14 days after the big race to see if infections developed. (a) What type of experimental design did the researchers use? Why is this design preferable in this setting? Give one reason. (b) Explain the purpose of the random assignment. (c) The report of the study said: Sixty-eight percent of the runners in the placebo group reported the development of symptoms of upper respiratory tract infection after the race; this was significantly more than that reported by the vitamin Csupplemented group (33%).63 Explain to someone who knows no statistics why significantly more means there is good reason to think that vitamin C works. s Know when a matched pairs experimental design is appropriate and how to implement such a design.