Table 1.

Statistical analysis for the results from Plackett–Burman experimental design

Model term	Coefficient estimate	Computed t value	p value	Confidence level (%)
(a) Coefficient values, t and p value for each variable
Intercept	0.33265	51.00	0*	100
CMC (X1)	0.11625	17.82	0*	100
Yeast extract (X2)	0.04215	6.46	0*	100
Peptone (X3)	0.02675	4.10	0.001*	99.9
K2HPO4 (X4)	0.00755	1.16	0.268	73.2
MgSO4·7H2O (X5)	−0.01105	−1.69	0.114	88.6
NaCl (X6)	0.00755	1.16	0.268	73.2

Variable	SS	DF	MS	F value	p value
					prob > F
(b) ANOVA for the model
Constant	0.325	6	0.0541	63.62	0
CMC (X1)	0.27	1	0.27	317.59	0
Yeast extract (X2)	0.0355	1	0.0355	41.75	0
Peptone (X3)	0.0143	1	0.0143	16.82	0.001
K2HPO4 (X4)	0.00114	1	0.00114	1.34	0.268
MgSO4·7H2O (X5)	0.00244	1	0.00244	2.87	0.114
NaCl (X6)	0.00114	1	0.00114	1.16	0.268
Residual	0.0111	13	0.000851	1.34
Total	0.336	19

DF degrees of freedom, SS sum of squares, MS mean square

* Significant p values, p ≤ 0.05; R² = 0.9671; predicted R² = 0.9220; adjusted R² = 0.9519