Question: Imagine that a sports researcher wanted to quantify the relation between miles run in training per week and finish time for a 5-kilometer race.
a. If the researcher studied a representative sample of North American adults, would you expect to find a relation between training and time? Would it be positive or negative? Explain.
b. If the researcher studied only those who run more than 25 miles per week, would you expect to find a relation between training and time? Would it be positive or negative?
c. Explain why the researcher might find very different results in these two scenarios even when using the same two variables.