Trey and Randall are conducting an experiment to test the effects of watering plants with deionized water compared to tap water. They take 20 plants of the same size and species, kept in the same area in front of a large window of their classroom, and water half with tap water and half with deionized water. All plants receive the same amount of water daily for three weeks. The plants watered with tap water grew an average of two inches taller. When they were finished, they reported their results in the school newspaper.