Chapter 3.4, Problem 60PB

Age a confounder? A study observes that the subjects in the study who say they exercise regularly reported only half as many serious illnesses per year, on the average, as those who say they do not exercise regularly. One paragraph in the results section of an article about the study starts out, “We next analyzed whether age was a confounding variable in studying this association.”

1. a. Explain what this sentence means and how age could potentially explain the association between exercising and illnesses.
2. b. If age was not actually measured in the study and the researchers failed to consider its effects, could it be a confounding variable or a lurking variable? Explain the difference between a lurking variable and a confounding variable.