Table 3.
Significance test for regression coefficient.
| Factor | Coefficient estimate | df | Standard error | 95% CI low | 95% CI high | F value | p-value Prob > F |
|---|---|---|---|---|---|---|---|
| Intercept | 80.0300 | 1 | 0.7643 | 78.3909 | 81.6692 | 15.6101 | <0.0001 |
| X1 | −3.0833 | 1 | 0.4933 | −4.1414 | −2.0253 | 39.0645 | <0.0001 |
| X2 | 1.2258 | 1 | 0.4933 | 0.1678 | 2.2839 | 6.1745 | 0.0262 |
| X3 | −0.1483 | 1 | 0.4933 | −1.2064 | 0.9097 | 0.0904 | 0.7681 |
| X4 | 3.8692 | 1 | 0.4933 | 2.8111 | 4.9272 | 61.5142 | <0.0001 |
| X1X2 | 2.8450 | 1 | 0.8545 | 1.0124 | 4.6776 | 11.0862 | 0.0050 |
| X1X3 | −1.8850 | 1 | 0.8545 | −3.7176 | −0.0524 | 4.8668 | 0.0446 |
| X1X4 | 3.4100 | 1 | 0.8545 | 1.5774 | 5.2426 | 15.9268 | 0.0013 |
| X2X3 | −0.4800 | 1 | 0.8545 | −2.3126 | 1.3526 | 0.3156 | 0.5832 |
| X2X4 | −0.6475 | 1 | 0.8545 | −2.4801 | 1.1851 | 0.5742 | 0.4611 |
| X3X4 | 1.3900 | 1 | 0.8545 | −0.4426 | 3.2226 | 2.6464 | 0.1261 |
| X12 | 2.2996 | 1 | 0.6710 | 0.8605 | 3.7387 | 11.7454 | 0.0041 |
| X22 | 3.9483 | 1 | 0.6710 | 2.5092 | 5.3875 | 34.6256 | <0.0001 |
| X32 | 4.9020 | 1 | 0.6710 | 3.4630 | 6.3412 | 53.3741 | <0.0001 |
| X42 | 1.4758 | 1 | 0.6710 | 0.0367 | 2.9150 | 4.8378 | 0.0451 |
Factors found to have significant effects on the scavenging rate of DPPH free radicals (p ≤ 0.05); factors found to have highly significant effects on the scavenging rate of DPPH free radicals (p ≤ 0.01); factors found to have extremely significant effects on the scavenging rate of DPPH free radicals (p ≤ 0.001); factors found to have no significant effect on the scavenging rate of DPPH free radicals (p > 0.05).