Refer to Exercise 14.14. Despite failing to show that differences in the three types of fertilizer exist, the scientist continued to believe that there were differences, and that the differences were masked by the variation between the plots of land. Accordingly, he conducted another experiment. In the second experiment he found 20 three-acre plots of land scattered across the county. He divided each into three plots and applied the three types of fertilizer on each of the one-acre plots. The crop yields were recorded.

a. Can the scientist infer that there are differences between the three types of fertilizer?

b. What do these test results reveal about the variation between the plots?