If not, make adjustments to add or delete terms, keeping within the options bered within a complete second-order model. c. Once you have settled on a model for logPrice, produce similar graphs to those you found in (a). Has the log transformation helped with either the constant variance or normality conditions on the residuals? 3.25 More diamond prices. Refer to the complete second-order model you found for diamond prices in Exercise 3.23(d). Use a nested F-test to determine whether all of the terms in the model that involve the information on Depth could be removed as a group from the model without signif- icantly impairing its of fectiveness. 3.26 More diamond prices. The young couple described in in Example 3.11 has found a 0.5- carat diamond with a depth of 62% that they are interested in buying. Suppose that you decide to use the quadratic regression model for predicting theTotal Price of the diamond using Carat. The data are stored in Diamonds a. What average total price does the quadratic model predict for a 0.5-carat diamond? b. Find a 95% confidence interval for the mean total price of 0.5-carat diamonds. Write a sentence interpreting the interval in terms that will make sense to the young couple. c. Find a 95% prediction interval for the total price when a diamond weighs 0.5 carats. Write a sentence interpreting the interval in terms that will make sense to the young couple. d. Repeat the previous two intervals for the model found in part (b) of Exercise 3.24, where the response variable was logPrice. You should find the intervals for the log scale, but then exponentiale to give answers in terms of TotalPrice 3.27 First-year GPA. The First YearGPA