Out of the examples below, pick two variables that are measurable and can ask people about. The variables must be continuous. Try to pick two variables that you expect would covary.

a. Hours of sleep the night before and amount of fatigue

b. Hours of sleep and overall mental well-being

c. Exercise level the past week and energy levels

d. Quality of diet and energy levels

e. Hours worked the past week and energy levels

f. Hours worked the past week and stress levels