Which statement best defines the independent variable in an experiment?

• A. The variable that the experimenter deliberately changes.
• B. The variable that is measured in response to the changes.
• C. The variable kept constant throughout the experiment.
• D. The variable that represents the final outcome.

Answer: (A)

The independent variable is the factor you deliberately change to see how it affects something else in the experiment. You set it at different values (for example, different amounts of light or different temperatures) to observe what happens to the outcome you’re measuring. The thing you measure in response is the dependent variable, and the variables you keep constant are the controlled variables, used to ensure a fair test. So the statement that describes changing the variable on purpose is the best fit.