11.53 ESTIMATING REPAIR AND REPLACEMENT COSTS OF WATER PIPES. Refer to the IHS Journal of Hydraulic Engineering (September 2012) study of water pipes susceptible to breakage, Exercises 11.21 (p. 640) and 11.37 (p. 648). Recall that civil engineers used simple linear regression to model the ratio of repair to replacement cost of commercial pipe (y) as a function of the diameter (x, in millimeters) of the pipe. The Minitab printout of the analysis is reproduced below. Are the engineers able to conclude (at ?=.05) that the cost ratio increases linearly with pipe diameter? If so, provide a 95% confidence interval for the increase in cost ratio for every 1-millimeter increase in pipediameter.?Yes; (.0041, .0055)

Regression Analysis: RATIO versus DIAMETER Regression Equation RATIO = 6.678 + 0.004786 DIAMETER Coefficients Term Coef SE Coef T-Value P-Value VIF Constant 6.678 0.121 55.29 0.000 DIAMETER 0.004786 0.000322 14.87 0.000 1.00 Model Summary S R-sq R-sq(adj) R-sq(pred) 0.221034 95.26% 94.83% 92.09% Analysis of Variance Source DF Adj SS Adj MS F-Value P-Value Regression 1 10.8067 10.8067 221.20 0.000 DIAMETER 1 10.8067 10.8067 221.20 0.000 Error 11 0.5374 0.0489 Total 12 11.3441