In November 2010, an article titled “Frequency of Colds Dramatically Cut with Regular Exercise” appeared in Medical News Today. Th e article was based on the findings of a study by researchers Nieman et al. (British Journal of Sports Medicine, 2010) that followed 1,002 people aged 18–85 years for 12 weeks, asking them to record their frequency of exercise (5 or more days a week? Yes or No) as well as incidences of upper respiratory tract infections (Cold during last week? Yes or No).
a. Identify the explanatory variable in this study. Also classify this variable as categorical or quantitative.
b. Identify the response variable in this study. Also classify this variable as categorical or quantitative.
c. Identify a confounding variable that provides an alternative explanation for the lower frequency of colds among those who exercised 5 or more days per week, compared to those who were largely sedentary.