Suppose you’re evaluating the effect of compost types on the…
Suppose you’re evaluating the effect of compost types on the growth rate of ornamental trees in a public garden. The growth rate of the ornamental trees varies with sunlight, soil drainage, and compost quality. You have batches of 3 different types of compost and 48 ornamental trees ready for planting. You have three available planting areas, one with plentiful sunlight and well-drained soil, one with shade and well-drained soil, one with shade and poorly-drained soil, and one with shade and well-drained soil. Which of the following experimental approaches would prevent sunlight and soil drainage from confounding the effects of the compost type? I) Use each of the 3 compost types in a different planting area II) Use all of the compost types in one of the planting areas III) Use all three compost types in all 4 planting areas