The Independent Variable: this is a variable that you intentionally change. In the case of our tomato plant experiment, it would be the brightness of the light in Tray #1.

The Dependent Variable: this is the difference between the two parts of the experiment that happens when the independent variable is changed. In this case, it would be the size of the tomatoes in Tray #1. So you turn the up the lights in Tray #1 (the independent variable) and the tomatoes get bigger (dependent variabl