Suppose that you want to test the effects of different dishwashing detergents on dishes that have food stuck to them. To test the differences, you wash three loads of the same dishes, each with a different type of detergent, all in warm water. You also wash a fourth load of dishes with only warm water.

What is the control in this experiment?



using different types of detergent



washing the dishes in warm water only



finding how clean the dishes get depending upon which detergent is used