Table 4. Effect estimates for the fitted quadratic polynomial model for chlorpyrifos degradation.

Term	Estimate	Standard Error	t Value	Pr > | t | *
X 1	−1.1843	1.1903	−0.9950	0.3379
X 2	−7.5036	1.1903	−6.3041	0.0001
X 3	7.8861	1.1903	6.6254	0.0001
X 1 X 1	−3.1131	1.1035	−2.8211	0.0144
X 1 X 2	−0.0950	1.5552	−0.0611	0.9522
X 1 X 3	0.3650	1.5552	0.2347	0.8181
X 2 X 2	−12.7085	1.1035	−11.5167	0.0001
X 2 X 3	1.1850	1.5552	0.7620	0.4597
X 3 X 3	−5.4890	1.1035	−4.9742	0.0002

^* P Level less than 0.05 indicate the model terms are significant.