d) Regress blood loss on duration of operation, and compute residuals for blood loss (with linear effects of duration of operation removed). Regress weight on duration of operation, and compute residuals for weight (with linear effects of duration of operation removed). Construct a scatter diagram of the residuals for blood loss versus the residuals for weight. Determine the same regression line, and verify that slope of this line is equal to the partial regression coefficient for weight, determined in the previous subproblem.