solution

Repair and replacement costs of water pipes. Refer to the IHS Journal of Hydraulic Engineering (September 2012) study of water pipes, Exercise 11.21 (p. 655). Refer, again, to the Minitab simple linear regression printout (p. 655) relating y = the ratio of repair to replacement cost of commercial pipe to x = the diameter (in millimeters) of the pipe.

a. Locate the value of s on the printout.

b. Give a practical interpretation of s

Exercise 11.21

Repair and replacement costs of water pipes. Refer to the IHS Journal of Hydraulic Engineering (September 2012) study of water pipes, Exercise 11.12 (p. 646). Recall that a team of civil engineers used regression analysis to estimate y = the ratio of repair to replacement cost of commercial pipe. The independent variable in the regression analysis was x = the diameter (in millimeters) of the pipe. Data for a sample of 13 different pipe sizes are provided in the table, followed by a Minitab simple linear regression printout.

a. Find the least squares line relating ratio of repair to replacement cost (y) to pipe diameter (x) on the printout.

b. Locate the value of SSE on the printout. Is there another line with an average error of 0 that has a smaller SSE than the line, part a? Explain.

c. Interpret, practically, the values ₀ and ₁.

d. Use the regression line to predict the ratio of repair to replacement cost of pipe with a diameter of 800 millimeters.

e. Comment on the reliability of the prediction, part d.

 

Exercise 11.12

Estimating repair and replacement costs of water pipes. Refer to Exercise 2.124 (p. 131). A team of civil engineers used simple linear regression analysis to model the ratio of repair to replacement cost of commercial pipe as a function of the pipe’s diameter. (IHS Journal of Hydraulic Engineering, September 2012.)

a. In this study, identify the dependent and independent variables.

b. Explain why a probabilistic model is more appropriate than a deterministic model.

c. Write the equation of the straight-line, probabilistic model

Exercise 2.124

Repair and replacement costs of water pipes. Pipes used in a water distribution network are susceptible to breakage due to a variety of factors. When pipes break, engineers must decide whether to repair or replace the broken pipe. A team of civil engineers estimated the ratio of repair to replacement cost of commercial pipe based on the diameter (in millimeters) of the pipe. (IHS Journal of Hydraulic Engineering, September 2012.) Data for a sample of 13 different pipe sizes are provided in the table. Use a scatterplot to aid the engineers in detecting a trend in the data. Does it appear that ratio of repair to replacement cost is strongly associated with pipe size?