In а clаssrооm full оf children, аdolescents, and adults, the effects of caffeine on reaction time were measured. One group of individuals was given caffeine-free cola to drink. The second had 10 mg of caffeine cola beverage. The third had 20 mg of caffeine cola beverage. Please select in the correct order: the dependent variable, the independent variable, the controlled variable (standardized variable), and the control.