Students noticed that, since the time that grass began to grow on a barren hillside, and water seemed to wash down the slope into the school yard during a rainstorm . The students thought that the grass helped hold the soil in place on the slope. The students predicted that more soil would wash down a slope without grass than a slope covered with grass. To find out if they were correct , the students conducted an experiment with three identical rectangular pans of soil. In pan 1 they planted grass seed and allowed it to grow to several centimeters tall. The students filled pan 2 with only soil. Then they took pan and pan 2and propped up at one end of each pan 15 cm high to create a slope . Pan 3, also filled with only soil, was propped up at one end at one end to create a slope . Students poured equal amounts of water on the raised end of each pan and the students recorded their observations . Which steps in the experimental method are missing from the description above?