What is the independent variable in an experiment?

• A. The outcome that may change in response to manipulations of the independent variable.
• B. The variable that is kept constant.
• C. The experimental factor that is manipulated; the variable whose effect is being studied.
• D. The group that receives no treatment.

Answer: (C)

The independent variable is the factor you deliberately change to see if it causes an effect. It’s the experimental factor that you manipulate, and it’s the variable whose impact you’re studying. The result you measure that may change in response to that manipulation is the dependent variable. Variables kept constant are controls, used to prevent other factors from influencing the outcome, and the group that receives no treatment is the control group, used for comparison. So the description that fits is the experimental factor that is manipulated; the variable whose effect is being studied.