Independent Variable. The variable that the scientist changes during the experiment is the independent variable. Think of the experiment as a cause and effect exercise. The independent variable is the cause factor. For example, to test the hypothesis that a seed needs light to germinate, the independent variable would be whether the seed was left exposed to light or covered with soil. If you hypothesize that Cub Scout pinewood derby cars are faster when the weight is near the rear, the placement of the weight is the independent variable.