Dr. Warren is testing the link between the consumption of caffeine and a person’s memory. She randomly divides 300 participants into three groups and gives each participant an energy drink to consume. Some of the drinks have high levels of caffeine, some have medium amounts, and some have none at all—but they all taste the same. About 30 minutes later, she has the participants play a memory game on the computer where they have to match faces and names together. At the end of the game, the computer thanks them for playing, and their scores are sent to Dr.

Warren’s lab. The dependent variable in the experiment is

a. how quickly the participants matched the names and faces.

b. the participants’ scores from the memory game.

c. the amount of caffeine they consumed.

d. their explanations about how they played the game.

e. the amount of caffeine they consume in a typical week.