Priya is conducting an experiment to see if people are more anxious when they're in a crowd of people or if they're alone. She divides her participants into two groups. With one group she has all of her participants take an anxiety questionnaire together in one small room. With the other group of participants she has them take the anxiety questionnaire by themselves, one at a time, in the same room. She then looks at the anxiety scores of every participant to see if they are influenced by her two different conditions. In this experiment, what is the independent variable