Table 1. Coded and uncoded values of factors.
| Parameters | Symbols | Coded values | ||
| −1 | 0 | 1 | ||
| Ethanol concentration (v/v, %) | X1 | 70 | 80 | 90 |
| Extraction time (h) | X2 | 4 | 7 | 10 |
| RES (min−1) | X3 | 0 | 0.02 | 0.04 |
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