Which variable is not controlled or manipulated by the researcher?

The dependent variable is the correct answer because it is the outcome that is measured in an experiment. Researchers observe how changes in the independent variable (the one they manipulate) affect the dependent variable. Unlike the independent variable, which is deliberately changed, the dependent variable is not controlled or manipulated directly by the researcher; instead, it is the variable that responds to those changes.

In contrast, the independent variable is controlled by the researcher to determine its effect, while controlled variables are kept constant to eliminate their influence on the dependent variable. The term "response variable" is often used interchangeably with "dependent variable," reinforcing that it reflects the outcome based on changes made to the independent variable. Therefore, understanding the roles of these variables is crucial in experimental design and data analysis.