Table 5.

Statistical analysis of face-centered central composite design showing coefficient values, main effect, t-test and P-values.

Variables	Coefficients	Main effect	t – student’s test	P-Value
Intercept	77.13	154.26	40.06	0.0000
X2	0.66	1.31	0.37	0.7185
X8	3.30	6.60	1.86	0.0921
X9	0.77	1.55	0.44	0.6718
X2X8	4.42	8.84	2.23	0.0497
X2X9	−3.87	−7.75	−1.96	0.0790
X8X9	−6.62	−13.24	−3.34	0.0075
X2X2	−37.08	−74.15	−10.98	0.0000
X8X8	−7.35	−14.69	−2.18	0.0547
X9X9	−12.93	−25.85	−3.83	0.0033
Analysis of variance (ANOVA)
	Degree of freedom	Sum of squares	Mean sum of squares	F - Fisher’s function	Significance F ( P -value)
Regression	9	13804.60	1533.844	48.89	4.33737E-07
Residual	10	313.73	31.37
Total	19	14118.32

X₂ the coded value of incubation time, X₈ the coded value of starch and X₉ the coded value of L-asparagine. Multiple R 0.9888, R Square 0.9777, Adjusted R Square 0.957.