In experimental design, a dependent variable is a variable whose values in different treatment conditions are compared. For example, in a study of how different dosages of a drug are related to the severity of symptoms of a disease, a measure of the severity of the symptoms of the disease is a dependent variable and the administration of the drug in specified doses is the independent variable. In simple terms the independent variable will cause an apparent change in the dependent variable, hence it needs a catalyst in order to change.