Table 2 Cross-validation results.
Stratum | Cross validation | Kriging | IDW | Thin plate spline | Regular spline function |
|---|---|---|---|---|---|
Z0 | Average error | 0.845 | 1.177 | 0.979 | 0.951 |
Root mean square | 1.144 | 1.600 | 1.251 | 1.286 | |
Z1 | Average error | 1.591 | 2.203 | 2.584 | 2.225 |
Root mean square | 2.132 | 2.852 | 3.124 | 2.809 | |
Z2 | Average error | – | 3.029 | 3.136 | 2.859 |
Root mean square | – | 3.805 | 4.110 | 3.711 | |
Z3 | Average error | – | 5.442 | 5.943 | 5.646 |
Root mean square | – | 6.523 | 7.131 | 6.744 | |
Z4 | Average error | – | 5.714 | 9.198 | 6.419 |
Root mean square | – | 6.783 | 10.422 | 6.657 | |
Z5 | Average error | – | 5.715 | 6.328 | 4.585 |
Root mean square | – | 5.581 | 7.503 | 5.766 |
