Return to the situation of Exercise 3 of Section 4.1(P 140. 3) and the polymer molecular weight study of R. Harris. (a) Find LaTeX: s_{LF} s L F for these data. What does this intend to measure in the context of the engineering problem? (b) Plot both residuals versus LaTeX: x x and the standardized residuals versus LaTeX: x x . How much difference is there in the appearance of these two plots? (c) Give a 90% two-sided confidence interval for the increase in mean average molecular weight that accompanies a LaTeX: 1^{^\circ}C 1 ∘ C increase in temperature here.