Researcher Smith collected data on the growth of 20 elephants from 5 zoos fed 4 different diets. Each elephant is housed in a separate cage, and not surprisingly, there is only room for 4 elephant cages at each zoo. Each of the 4 elephants at each zoo are randomly assigned a different diet, so that each of the four diets was fed to at least one elephant in each zoo. The data collected indicate which diet each elephant was given and the resulting (weight change in kg). Choose the correct approach to test the hypothesis that the different diets influence elephant growth differently, regardless of which zoo elephants are housed in, and explain your choice.