251. MA
Moving average
i.e.,
Always stationary. Invertible if roots of lie outside the unit circle.
Parameters: , ,
Orders:
Example:
Given
- Order:
- Parameters: ,
- Initial innovation:
- Data:
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | |
| 12 | 10 | 8 | 11 | 14 | 12 | 9 | 13 | 16 | 14 | 11 | 15 | 18 | 16 | 13 | 17 |
Step 1 — formula
Substitute into the MA recursion:
Forecast (set ):
Innovation:
Step 2 — apply at
Plug in , , and :
Step 3 — iterate
Each row uses the previous innovation . Values rounded to 4 decimal places.
| 1 | 12 | ||
| 2 | 10 | ||
| 3 | 8 | ||
| 4 | 11 | ||
| 5 | 14 | ||
| 6 | 12 | ||
| 7 | 9 | ||
| 8 | 13 | ||
| 9 | 16 | ||
| 10 | 14 | ||
| 11 | 11 | ||
| 12 | 15 | ||
| 13 | 18 | ||
| 14 | 16 | ||
| 15 | 13 | ||
| 16 | 17 | ||
| 17 | — | — |
Like AR(1), MA(1) cannot capture the trend or seasonality in .