You want to test the effects of different potting soils on t…
You want to test the effects of different potting soils on the rate of plant growth. You want to test Miracle Gro, Earthgro, and untreated dirt from your garden at home. You decide to have 10 pots of each of the potting substrates and use tomato plants in your experiment. Each day you measure the height of the tomato plants from the surface of the substrate to the tip of the tomato plant stalk. Which statement from the experimental description above would be a controlled variable?