A Team of Researchers Investigated the Effects of Fertilizer on the Growth

Essay

A team of researchers investigated the effects of fertilizer on the growth of forest trees. They used an old Christmas tree plantation with pine trees of the same species and age, dividing it into plots and testing growth rates at different levels of fertilization. They calculate averages from their treatment groups, and see that the low-fertilizer group had a higher growth rate than the high-fertilizer group. They conclude that applying a small amount of fertilizer always causes all trees to grow faster than applying a large amount. Is this conclusion valid? Explain.