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.

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d and e

## 11.21 Repair and Replacement Costs of Water Pipes

**Context:**
Refer to the IHS Journal of Hydraulic Engineering (September 2012) study of water pipes. 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 below, followed by a Minitab simple linear regression printout.

**Data Table:**

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

**Source:**
Based on ISH Journal of Hydraulic Engineering, Volume 18, Issue 3, pp. 241–251. Copyright: September 2012.

**Tasks:**

a. **Linear Regression Line**: Use the printout to find the least squares line relating the ratio of repair to replacement cost (\( y \)) to pipe diameter (\( x \)).

b. **Sum of Squares due to Error (SSE)**: Locate the SSE on the printout. Consider if there is another line with an average error of 0 that has a smaller SSE than the line in part a. Explain your findings.

c. **Interpret Coefficients**: Provide a practical interpretation of \(\beta_0\) and \(\beta_1\) values.

d. **Prediction**: Use the regression line to predict the ratio for a pipe with a diameter of 800 millimeters.

e. **Reliability of Prediction**: Comment on the reliability of the prediction made in part d.

**Regression Analysis Summary:**

- **Analysis of Variance:
Transcribed Image Text:## 11.21 Repair and Replacement Costs of Water Pipes **Context:** Refer to the IHS Journal of Hydraulic Engineering (September 2012) study of water pipes. 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 below, followed by a Minitab simple linear regression printout. **Data Table:** | Diameter (mm) | Ratio | |---------------|-------| | 80 | 6.58 | | 100 | 6.97 | | 125 | 7.39 | | 150 | 7.61 | | 200 | 7.92 | | 250 | 7.92 | | 300 | 8.20 | | 350 | 8.42 | | 400 | 8.60 | | 450 | 8.97 | | 500 | 9.31 | | 600 | 9.47 | | 700 | 9.72 | **Source:** Based on ISH Journal of Hydraulic Engineering, Volume 18, Issue 3, pp. 241–251. Copyright: September 2012. **Tasks:** a. **Linear Regression Line**: Use the printout to find the least squares line relating the ratio of repair to replacement cost (\( y \)) to pipe diameter (\( x \)). b. **Sum of Squares due to Error (SSE)**: Locate the SSE on the printout. Consider if there is another line with an average error of 0 that has a smaller SSE than the line in part a. Explain your findings. c. **Interpret Coefficients**: Provide a practical interpretation of \(\beta_0\) and \(\beta_1\) values. d. **Prediction**: Use the regression line to predict the ratio for a pipe with a diameter of 800 millimeters. e. **Reliability of Prediction**: Comment on the reliability of the prediction made in part d. **Regression Analysis Summary:** - **Analysis of Variance:
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