0.000 Days After Injection 0.041250 0.003000 13.75 0.000 S 0.0777817 R-Sq 96.9% R-Sq(adj) 96.4%

c. Use the Minitab output to predict average tumor size 30 days after injection of cancer cells for a mouse that received water supplemented with 0.2% PFE.

d. Residual plots of the residuals from the least-squares line using the untransformed data and using y and x are shown at the bottom of the page in Figure EX5.44.
What feature of the residual plot for the original data suggests that the least-squares line is not the best way to describe the relationship between y and x? In what way does the residual plot for the transformed data suggest that a line is a reasonable description of the relationship for the transformed data (y and x)?