Which statement best defines an independent variable with an example?

• A. The outcome measured in an experiment; for example, plant height.
• B. The factor manipulated in an experiment; for example, the amount of sunlight a plant receives.
• C. The control group.
• D. The method of data analysis.

Answer: (B)

An independent variable is the factor you deliberately change in an experiment to test its effect. It is the cause you manipulate, while the outcome you measure is the dependent variable. Here, the amount of sunlight a plant receives is something you control and vary, so it serves as the independent variable. By changing sunlight and then measuring how tall the plant grows, you’re testing how this factor influences growth—the dependent variable. The other options describe what you measure (the outcome) or the baseline for comparison (the control group) or how you analyze the data, none of which are the factor you actively manipulate.