Table 2.
impact factors and level distribution.
| Number of levels |
Influencing factor |
|||
|---|---|---|---|---|
| A | B | C | D | |
| 1 | 292 | −6 | 12 | 330 |
| 2 | 302 | −5 | 13 | 340 |
| 3 | 312 | −4 | 14 | 350 |
| 4 | 322 | −3 | 15 | 360 |
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