Table 2.
Exponential smoothing model parameters
| Metal | Model | Parameters | Coefficient | Standard error | T | P-value |
|---|---|---|---|---|---|---|
| Aluminum | Holt | Alpha (level) | 0.700 | 0.188 | 3.729 | 0.001* |
| Gamma (trend) | 0.000 | 0.165 | 0.000 | 1.000 | ||
| Brown | Alpha (level and trend) | 0.299 | 0.066 | 4.502 | 0.000* | |
| Damped | Alpha (level) | 0.715 | 0.194 | 3.677 | 0.001* | |
| Gamma (trend) | 0.000 | 0.171 | 0.000 | 1.000 | ||
| Phi (trend damping factor) | 1.000 | 0.035 | 28.268 | 0.000* | ||
| Copper | Holt | Alpha (level) | 1.000 | 0.215 | 4.652 | 0.000* |
| Gamma (trend) | 0.000 | 0.092 | 0.002 | 0.999 | ||
| Brown | Alpha (level and trend) | 0.550 | 0.090 | 6.084 | 0.000* | |
| Damped | Alpha (level) | 1.000 | 0.223 | 4.493 | 0.000* | |
| Gamma (trend) | 0.000 | 0.142 | 0.000 | 1.000 | ||
| Phi (trend damping factor) | 0.999 | 0.028 | 35.658 | 0.000* | ||
| Lead | Holt | Alpha (level) | 0.804 | 0.179 | 4.491 | 0.000* |
| Gamma (trend) | 0.000 | 0.038 | 0.000 | 1.000 | ||
| Brown | Alpha (level and trend) | 0.394 | 0.071 | 5.527 | 0.000* | |
| Damped | Alpha (level) | 0.814 | 0.186 | 4.386 | 0.000* | |
| Gamma (trend) | 0.001 | 0.106 | 0.005 | 0.996 | ||
| Phi (trend damping factor) | 0.993 | 0.033 | 30.194 | 0.000* | ||
| Iron | Holt | Alpha (level) | 1.000 | 0.211 | 4.748 | 0.000* |
| Gamma (trend) | 0.000 | 0.122 | 0.004 | 0.997 | ||
| Brown | Alpha (level and trend) | 0.770 | 0.093 | 8.297 | 0.000* | |
| Damped | Alpha (level) | 0.900 | 0.838 | 1.073 | 0.292 | |
| Gamma (trend) | 0.999 | 4.221 | 0.237 | 0.815 | ||
| Phi (trend damping factor) | 0.500 | 0.803 | 0.623 | 0.538 | ||
| Nickel | Holt | Alpha (level) | 0.999 | 0.198 | 5.050 | 0000* |
| Gamma (trend) | 0.000 | 0.131 | 0.000 | 1.000 | ||
| Brown | Alpha (level and trend) | 0.392 | 0.074 | 5.318 | 0.000* | |
| Damped | Alpha (level) | 1.000 | 0.205 | 4.880 | 0.000* | |
| Gamma (trend) | 0.001 | 0.161 | 0.006 | 0.995 | ||
| Phi (trend damping factor) | 0.999 | 0.062 | 16.173 | 0.000* | ||
| Tin | Holt | Alpha (level) | 0.600 | 0.199 | 3.023 | 0.005* |
| Gamma (trend) | 0.000 | 0.134 | 0.000 | 1.000 | ||
| Brown | Alpha (level and trend) | 0.650 | 0.219 | 2.963 | 0.006* | |
| Damped | Alpha (level) | 0.650 | 0.219 | 2.963 | 0.006* | |
| Gamma (trend) | 0.001 | 0.144 | 0.007 | 0.994 | ||
| Phi (trend damping factor) | 1.000 | 0.013 | 74.277 | 0.000* | ||
| Zinc | Holt | Alpha (level) | 1.000 | 0.190 | 5.252 | 0.000* |
| Gamma (trend) | 0.000 | 0.073 | 0.002 | 0.998 | ||
| Brown | Alpha (level and trend) | 0.188 | 0.048 | 3.888 | 0.000* | |
| Damped | Alpha (level) | 1.000 | 21.340 | 0.047 | 0.963 | |
| Gamma (trend) | 1.000 | 446.623 | 0.002 | 0.998 | ||
| Phi (trend damping factor) | 0.100 | 21.237 | 0.005 | 0.996 |
*p < 0.05 model parameter coefficient was significant