Table 3.
Summary outcomes of best ARIMA models.
| Appropriate model | Coefficient estimate |
Fitting model |
Ljung Box-test |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| AR1 | AR2 | AR3 | AR4 | MA1 | MA2 | MA3 | AIC | BIC | Q | p-value | |
| Pre COVID-19 | |||||||||||
| Oil-ARIMA | −0.440** | 0.373** | 0.114 | −0.373** | 0.775*** | – | 369.1 | 381.57 | 4.4721 | 0.4836 | |
| Coal-ARIMA | −0.801*** | – | 1.400*** | 0.1709 | −0.427 | 382.56 | 392.95 | 8.197 | 0.224 | ||
| Natural gas-ARIMA | −0.624*** | – | 0.941*** | – | 361.85 | 368.08 | 4.842 | 0.774 | |||
| Post COVID-19 | |||||||||||
| Oil-ARIMA | 0.251* | – | – | 354.79 | 358.53 | 7.175 | 0.618 | ||||
| Coal-ARIMA | −0.167** | −0.038* | – | 0.338** | – | 335.44 | 342.92 | 9.063 | 0.248 | ||
| Natural gas-ARIMA | 0.326* | – | – | 297.24 | 300.98 | 12.402 | 0.192 | ||||
Asterisks *, **, and *** refer to the significance level at 10, 5, and 1%. Also, the Ljung-Box analysis was employed to evaluate the residuals of the best appropriate methods.
Source: Author's calculation.