Which of the following best describes the independent variable in an experiment?

The independent variable in an experiment is the one that is intentionally manipulated by the researcher to observe its effects on another variable, known as the dependent variable. This manipulation allows the researcher to establish a cause-and-effect relationship between the independent and dependent variables. By altering the independent variable, the researcher observes any resulting changes, enabling insights into how different conditions or treatments may impact outcomes.

For instance, if a researcher is testing the effect of different amounts of sunlight on plant growth, the amount of sunlight would be the independent variable since it is the factor that the researcher can control and change. The results, such as the height of the plants, would then be measured to determine the impact of the manipulated variable.

In contrast, other options describe characteristics of different types of variables: the variable that remains unchanged refers to a controlled variable, the measurable outcome refers to the dependent variable, and predictability generally pertains to established relationships rather than specific variable roles in an experimental design.