Physical fitness and academic performance In a study by Karen Rod Enroth, "A study of the relationship between physical fitness and academic performance", conducted among students of the fourth and fifth grade in a rural northeast Georgia elementary school, it was found that students who are more involved in physical education class are more likely to have high grades.

a. What is the population of interest for this survey?

b. Describe why this is an observational study.

c. Identify a lurking variable in this study.