In an experiment, which statement best describes a control variable?

In an experiment, which statement best describes a control variable?

• A. It is the variable you change on purpose
• B. It is the variable you measure
• C. It is a factor kept the same in all trials
• D. It is the data you analyze

Answer: (C)

In experiments, scientists look for how one factor affects another. A control variable is a factor kept the same in all trials so that it cannot explain any differences you observe. Keeping these conditions constant helps you see whether changes come from the thing you’re actively testing—the independent variable—rather than from other influences. For example, when checking how sunlight affects plant growth, you would keep soil type, amount of water, pot size, and ambient temperature the same across all trials, changing only the amount of sunlight. The variable you change on purpose is not a control variable, and the variable you measure to gather results is the dependent variable. The data you analyze are the results you collect, not a variable kept constant.

In experiments, scientists look for how one factor affects another. A control variable is a factor kept the same in all trials so that it cannot explain any differences you observe. Keeping these conditions constant helps you see whether changes come from the thing you’re actively testing—the independent variable—rather than from other influences. For example, when checking how sunlight affects plant growth, you would keep soil type, amount of water, pot size, and ambient temperature the same across all trials, changing only the amount of sunlight. The variable you change on purpose is not a control variable, and the variable you measure to gather results is the dependent variable. The data you analyze are the results you collect, not a variable kept constant.