ree size measures as diameter at breast height (DBH) Data for longleaf pine trees in two parts of a tract of land are compared. Suppose that you are planning a study in which you will measure the diameters of longleaf pine trees. Assume that the standard deviation for both parts is 20 cm. Suppose that a difference in mean DBH of 10 cm or more would be important to detect. You will use a t statistic and a two-sided alternative for the comparison. Find the power if you randomly sample 20 trees from each area to be compared for a significance level of 5%. Do not use the normal approximation. You will need to find the non-centrality parameter, then use the appropriate t distribution to calculate your answer.