Which variable must be intentionally changed by the researcher in an experimental study?

In an experimental study, the variable that must be intentionally changed by the researcher is known as the independent variable. This is the factor that the researcher manipulates to observe its effect on another variable, typically the dependent variable. The independent variable is central to the hypothesis being tested, as it allows the researcher to analyze how variations in this variable influence outcomes.

By manipulating the independent variable, researchers can establish cause-and-effect relationships and determine whether changes in the dependent variable arise as a result of these manipulations. For example, if a researcher wants to test the effect of different amounts of sunlight on plant growth, the amount of sunlight would be the independent variable that the researcher changes.

Other variables mentioned, such as dependent and extraneous variables, play different roles in an experiment. The dependent variable is what is measured and is expected to change as a result of variations in the independent variable, while extraneous variables are outside influences that can affect the outcome but are not the focus of the study. Control variables are factors that researchers keep constant to ensure that the results are attributable only to the manipulation of the independent variable.