Determine the effect of fertilizer on plant growth. He purchased 9 identical plants and separated them into 3 groups. Group 1 did not receive fertilizer,
Group 2 received one teaspoon of fertilizer, and Group 3 received two teaspoons of
fertilizer. All the plants received the same amount of water and were placed in the
same location so they could receive the same amount of sunlight. What was the
outcome variable (dependent variable) in Kevin's experiment