Table 4.
Analysis of variance for the fitted quadratic polynomial model of extraction of glycyrrhizic acid.
| Source | DFa | Sum of squares | F-value | p-value |
|---|---|---|---|---|
| Regression | 9 | 30.1335 | 61.57 | 0.000 |
| Linear | 3 | 15.6342 | 95.83 | 0.000 |
| X1 | 1 | 10.8811 | 200.09 | 0.000 |
| X2 | 1 | 0.7373 | 13.56 | 0.001 |
| X3 | 1 | 4.0158 | 73.84 | 0.000 |
| Square | 3 | 9.2582 | 56.75 | 0.000 |
| X1X1 | 1 | 1.5775 | 48.01 | 0.000 |
| X2X2 | 1 | 3.5957 | 80.13 | 0.000 |
| X3X3 | 1 | 4.0850 | 75.12 | 0.000 |
| Interaction | 3 | 5.2411 | 32.12 | 0.000 |
| X1X2 | 1 | 0.0036 | 0.07 | 0.797 |
| X1X3 | 1 | 0.0708 | 1.30 | 0.259 |
| X2X3 | 1 | 5.1667 | 95.01 | 0.000 |
| Residual error | 50 | 2.7191 | – | – |
| Lack of fit | 5 | 0.4597 | 1.83 | 0.126 |
| Pure error | 45 | 2.2594 | – | – |
| Total | 59 | 32.8526 | – | – |
a
DF, degrees of freedom.