Estimating repair and replacement costs of water pipes.

Refer to the IHS Journal of Hydraulic Engineering

(Sept. 2012) study of water pipes susceptible to breakage, Exercise 11.28 (p. 628). Recall that civil engineers used simple linear regression to model y = the ratio of repair to replacement cost of commercial pipe as a function of x = the diameter (in millimeters) of the pipe.

The MINITAB printout of the analysis is reproduced LO9 

below. Are the engineers able to conclude (at a = .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 pipe diameter.

Transcribed Image Text:

Regression Analysis: RATO versus DIAMETER The regression equation is RATO 6.68 +0.00479 DIAMETER Predictor Constant Coef 6.6782 SE Coef I P 0.1208 55.29 0.000 DIAMETER 0.0047856 0.0003218 14.87 0.000 S = 0.221034 R-Sq = 95.3% R-Sq (adj) = 94.8% Analysis of Variance Source DF SS MS F P Regression 1 10.807 10.807 221.20 0.000 Residual Error 11 0.537 0.049 Total 12 11.344