Dr Brown Is Interested in Finding Out Whether Different Types

Multiple Choice

Dr Brown is interested in finding out whether different types of beverages and nicotine influence students' performance on a memory task. She randomly allocates 200 university students into three groups. Thirty minutes before the task, she asks Group A to drink 30ml of black coffee, Group B to drink 30ml of orange juice and Group C to drink 30ml of Coke. In addition, she makes sure that in each group half of the participants are regular cigarette smokers and smoke one cigarette 10 minutes before the memory task. How many independent variables are used in Dr Brown's experiment?

A) 1
B) 2
C) 3
D) 5