Use the following study to answer the following question. a researcher applies varying amounts of fertilizer (0, 2, 4, 8, 10 units) to 50 potted tomato plants. all other variables that may affect the outcome (watering, temperature, sunlight, plant size, etc) are kept from pot to pot. at the end of the growing season, the tomatoes grown on each plant are weighed to determine which fertilizer level produces the largest tomato yield. is the study presented above a controlled experiment?