Which variable is changed by a researcher to initiate a response in an experiment?

In experimental research, the variable that is manipulated by the researcher to observe its effect on another variable is known as the independent variable. When a researcher changes the independent variable, they are effectively creating different conditions or treatments to examine how these changes influence the response of other variables, particularly the dependent variable, which is the outcome that is measured.

For example, in a study examining the effects of different amounts of sunlight on plant growth, the amount of sunlight would be the independent variable. By altering this variable, the researcher can see how it affects the growth of the plants, which would be the dependent variable. The concept of the independent variable is fundamental to understanding experimental design, as it is the starting point for hypothesis testing and determining causal relationships.

Other options, such as control variables, are maintained at constant levels to ensure that any changes in the dependent variable are solely due to the manipulation of the independent variable, while random variables refer to fluctuations that can affect the outcome unpredictably, rather than being systematically controlled or manipulated in the experiment.