Which term describes a variable kept constant to isolate the effect of the independent variable?

Which term describes a variable kept constant to isolate the effect of the independent variable?

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

Answer: (D)

The key idea is that experiments aim to attribute changes in the outcome to the factor you deliberately vary. To do that clearly, you hold all other potential influences constant. That fixed factor is called a control variable. By keeping things like temperature, light, solvent amount, or sample size the same across trials, you ensure that any observed change in the dependent measure arises from the independent variable, not from some other factor. For example, if you study how concentration affects reaction rate, you would keep temperature and volume constant so the only thing changing is concentration. Random variability can still occur, but it’s managed by repeating trials and randomizing conditions; the dependent variable is what you measure, and the independent variable is what you deliberately change.

The key idea is that experiments aim to attribute changes in the outcome to the factor you deliberately vary. To do that clearly, you hold all other potential influences constant. That fixed factor is called a control variable. By keeping things like temperature, light, solvent amount, or sample size the same across trials, you ensure that any observed change in the dependent measure arises from the independent variable, not from some other factor. For example, if you study how concentration affects reaction rate, you would keep temperature and volume constant so the only thing changing is concentration. Random variability can still occur, but it’s managed by repeating trials and randomizing conditions; the dependent variable is what you measure, and the independent variable is what you deliberately change.