Final answer:
The independent variable is the variable that is manipulated or changed by the researcher, while the dependent variable is the variable that is measured to determine the effects of the independent variable.
Step-by-step explanation:
In experiments, the independent variable (IV) is the variable that is manipulated or changed by the researcher. In this case, the IV is whether the IV is either present or absent during the study. For example, if a study is investigating the effects of caffeine on sleep, the IV would be whether the participants consume caffeine or not. The dependent variable (DV) is the variable that is measured to determine the effects of the independent variable. In the caffeine example, the DV would be the quality or duration of sleep.