Table 5.

ANOVA and fit statistics comparing linear, two-factor interaction (2FI), and quadratic polynomial models.

Reponses	dry density (/)	Cohesion (kN/m2)	internal friction angle (°)	compressibility coefficient Cc (/)	Swelling coefficient Cg (/)
Model tested (1)	Linear polynomials
R2	0.9628	0.9594	0.9774	0.9662	0.9988
Adjusted R2	0.9594	0.9558	0.9754	0.9631	0.9986
Predicted R2	0.9433	0.9397	0.9705	0.9537	0.9983
Model F value	284.36	260.25	476.35	314.23	8852.15
Model P value	< 0.0001	< 0.0001	< 0.0001	< 0.0001	< 0.0001
Model remarks	Significant	Significant	Significant	Significant	Significant
Model tested (2)	Two-factor interaction (2FI)
R2	0.9979	0.9869	0.9775	0.9789	0.9988
Adjusted R2	0.9975	0.9843	0.9730	0.9746	0.9986
Predicted R2	0.9958	0.9796	0.9607	0.9632	0.9982
Model F value	2394.83	377.17	217.47	231.64	4282.00
Model P value	< 0.0001	< 0.0001	< 0.0001	< 0.0001	< 0.0001
Model remarks	Significant	Significant	Significant	Significant	Significant
Model tested (3)	Quadratic polynomials
Standard deviation	0.0031	0.9482	0.7020	0.0014	0.0004
Mean	1.66	31.69	14.81	0.1470	0.0399
R2	0.9979	0.9869	0.9775	0.9789	0.9988
Adjusted R2	0.9975	0.9843	0.9730	0.9746	0.9986
Predicted R2	0.9958	0.9796	0.9607	0.9632	0.9982
Adequate precision	125.8695	50.1427	38.6144	39.5951	171.3478
Model F value	2394.83	377.17	217.47	231.64	4282.00
Model P value	< 0.0001	< 0.0001	< 0.0001	< 0.0001	< 0.0001
Model remarks	Significant	Significant	Significant	Significant	Significant
model adopted	Quadratic	Quadratic	Quadratic	Quadratic	Quadratic

R² coefficient of determination, MSE mean square error, ANOVA analysis of variance.