Which statement best defines the dependent variable in an experiment?

• A. The variable that is measured for every change in the independent variable.
• B. The variable that the experimenter deliberately changes.
• C. The variable kept constant throughout the experiment.
• D. The sum of all measurements taken.

Answer: (A)

In an experiment you change one quantity and observe another to see how it responds. The dependent variable is the quantity you measure to see the effect of that change. For every value you set for the thing you deliberately change, you record a corresponding measurement of the outcome. That’s why the dependent variable is the measurement that varies with the independent variable, and it’s often shown on the vertical axis of a graph to show how it responds to changes in the other variable. The thing you deliberately change is the independent variable, not the dependent. The constants are kept the same to keep the test fair, and summing all measurements isn’t describing a variable but just a total. So, the statement that the dependent variable is the quantity you measure for every change in the independent variable best captures its role.