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 used regression analysis to estimate y = the ratio of repair to replacement cost of commercial pipe in the IHS Journal of Hydraulic Engineering (Sept.

2012). 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 b n 0 and b n 1.

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Diameter Ratio 80 6.58 100 6.97 125 7.39 150 7.61 200 7.78 250 7.92 300 8.20 350 8.42 400 8.60 450 8.97 500 600 700 9.31 9.47 9.72