In an experiment, which variable is intentionally changed to observe its effect?

• A. Dependent variable
• B. Control variable
• C. Extraneous variable
• D. Independent variable

Answer: (D)

In an experiment, you actively change a factor to see what effect it has on another outcome. That factor is the independent variable, the one you manipulate to observe changes in the result. The thing you measure in response is the dependent variable. You keep other factors the same (control variables) to ensure any observed effects come from the change you made, while extraneous variables are unwanted influences you try to prevent.

For example, if you’re testing how sunlight affects plant growth, the amount of sunlight is the independent variable, and plant height is the dependent variable. You’d keep soil, water, and temperature constant as control variables to isolate the effect of sunlight.