Estimating Methods, Variability, and Sampling for Drop-Test Data
Appendix (Continued)
Grid Spacing
Gpc data collected from a previous drop test, which used a grid with cups in a 10- by 10-foot spacing, were used for the following comparisons. The 10- by 10-foot spacing provided a data set that could be divided into subsets for cross validation. Two subsets were created with the points in a 20- by 10-foot spacing, and three subsets were created with the points in a 30- by 10-foot spacing. Figures 22 and 23 show examples of these subsets. Tables 10 to 14 display the cross validation tabular results. Figures 24 and 25 display the QQ-plots comparing distributions.

Figure 22The original 10-foot spacing was increased
to 20 feet to evaluate sampling density.

Figure 23The original 10-foot spacing was increased
to 30 feet to evaluate sampling density.
Table 10First comparison of observed gpc (gallons per hundred square feet) values from a 10- by 10-foot spacing with predicted values from a 20- by 10-foot spacing. MAE is mean absolute error and MSE is mean squared error.
| |
| |
TRUE |
Triangulation (gpc) |
| Mean |
1.534 |
1.509 |
| Standard deviation |
0.905 |
0.819 |
| Minimum |
0.037 |
0.068 |
| 1st quartile |
0.950 |
0.962 |
| Median |
1.380 |
1.419 |
| 3rd quartile |
2.008 |
2.052 |
| Maximum |
5.081 |
5.428 |
| Correlation |
|
0.905 |
| n |
319 |
319 |
|
| Summary statistics for error distribution |
| |
Triangulation (gpc) |
| Mean |
0.02483 |
| Standard deviation |
0.386 |
| Minimum |
-1.856 |
| 1st quartile |
-0.144 |
| Median |
-0.021 |
| 3rd quartile |
0.150 |
| Maximum |
2.206 |
| MAE |
0.246 |
| MSE |
0.149 |
| n |
319 |
|
Table 11Second comparison of observed gpc (gallons per 100 square feet) values from a 10- by 10-foot spacing with predicted values from a 20- by 10-foot spacing. MAE is mean absolute error and MSE is mean squared error.
| |
| |
TRUE |
Triangulation (gpc) |
| Mean |
1.524 |
1.550 |
| Standard deviation |
0.922 |
0.805 |
| Minimum |
0.040 |
0.093 |
| 1st quartile |
0.909 |
0.994 |
| Median |
1.412 |
1.411 |
| 3rd quartile |
2.012 |
2.071 |
| Maximum |
8.183 |
4.060 |
| Correlation |
|
0.893 |
| n |
308 |
308 |
|
| Summary statistics for error distribution |
| |
Triangulation (gpc) |
| Mean |
-0.02628 |
| Standard deviation |
0.416 |
| Minimum |
-1.044 |
| 1st quartile |
-0.201 |
| Median |
-0.035 |
| 3rd quartile |
0.096 |
| Maximum |
4.122 |
| MAE |
0.241 |
| MSE |
0.173 |
| n |
308 |
|
Grid spacing continued...
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