In an experiment, what is a dependent variable?

The dependent variable is the element of an experiment that researchers measure to observe any effects caused by the manipulation of the independent variable. In essence, it represents the outcome or response that the experiment seeks to understand as it changes in response to variations in the independent variable. For instance, if researchers are examining how different amounts of sunlight affect plant growth, the growth of the plants would be the dependent variable, as that is what they measure to see any differences resulting from the varying levels of sunlight exposure.

In contrast to this, the other options describe different types of variables. The controlled variable, for instance, refers to those factors that are kept constant to ensure that any observed effects on the dependent variable can be attributed solely to the changes made to the independent variable. Furthermore, a variable that affects the independent variable doesn't fit the definition of a dependent variable, as it implies a causal relationship that goes against the standard design where the independent variable is manipulated to see its effect. A variable that does not change would not qualify as it fails to measure any changes based on the experimental conditions, which is a core function of the dependent variable.