Table 1 Depiction of independent variable levels in both actual and coded formats
Variables (independent) | Signs | Levels of code | ||
|---|---|---|---|---|
− 1 | 0 | + 1 | ||
ML1 concentration (μg/l) | \({X}_{1}\) | 0 | 30 | 60 |
ML2 concentration (μg/l) | \({X}_{2}\) | 0 | 30 | 60 |
Temperature (°C) | \({X}_{3}\) | 20 | 35 | 50 |