Table 1.
Three levels of the three variables of the extraction process.
| Independent variables | Symbols | Coded levels | ||
|---|---|---|---|---|
| −1 | 0 | 1 | ||
| Ethanol concentration (%) | X 1 | 40 | 60 | 80 |
| Microwave power (W) | X 2 | 80 | 240 | 400 |
| Extraction time (min) | X 3 | 1 | 3 | 5 |
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