Which variable is deliberately changed by the researcher to test its effect?

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

Answer: (A)

In an experiment, the factor that researchers deliberately changes to see what happens is the independent variable. This is the input or treatment you apply in different conditions to learn how it influences the outcome. The thing you measure—the result or effect—is the dependent variable, because it depends on how you manipulated the independent variable. You also keep other factors the same across all trials, called control variables, so they don’t affect the outcome. A constant is a fixed value that isn’t varied to test an effect, so it isn’t the variable being tested. For example, if you’re exploring how sunlight affects plant growth, sunlight amount is the independent variable, plant height is the dependent variable, and factors like soil type and water are control variables.