Chirs wanted to test the effect of diet pills on how tall the tomato plants in his garden would grow. he took two pots, filled them with dirt from the same bag, and planted four tomato plants in each. he watered one planter with tap water, and he watered the other planter with tap water mixed with dissolved diet pills. the plants were in the same location to ensure they got same amount of sunlight, and the water was measured so that each pot received the same amount of water. he measured their height at the end of each week for eight weeks, and averaged the height of the four plants in each pot. he then graphed the result to show how the diet pills affected the height of the plants.
1: what is the independent variable of this experiment?