The Scientific Method Explained In an example experiment, if one tests at what temperature plants grow the best, the temperature would be the independent variable since one would want to test at multiple temperatures. A dependent variable is a variable that is dependent on another. Using our same example, growth would be the dependent variable because it is dependent on the temperature variable. Control variables are variables that remain constant, like what the plants are fed and when. It is important to hold variables constant, or "control" them, except for the independent variable, to isolate the effects of the independent variable. What does it mean to "control" an experiment? to regulate all variables except the one being tested to manipulate the data to fit the experiment to limit the number of observations