Teen athletes often wear ankle and knee braces to protect themselves from sports injuries.
a. Suppose the proportion of all teen athletes who suffer ankle and knee injuries is p0. The null hypothesis would state that the proportion p of teen athletes with ankle and knee braces who suffer such injuries is the same-H0 : p p0. State the alternative hypothesis, first in words and then mathematically, if we suspect that ankle and knee braces help protect against injuries.
b. A study of student athletes in 100 North Carolina high schools in the late 1990s found that "North Carolina teens who wore ankle and knee braces were 1.6 to 1.7 times more likely to become injured than their fellow athletes." Explain why there is no need to find a standardized sample proportion and a P-value to decide between the null and alternative hypotheses (from part [a]) in this case.
c. Before concluding that ankle and knee braces actually increase the likelihood of injury, possible confounding variables should be taken into account. Give at least one reason why someone wearing such a brace might be more susceptible to injury, besides the brace itself causing the injury.