From: Brette Pearl Spar Mable (BPSM): a potential recoverable catalyst as a renewable source of biodiesel from Thevetia peruviana seed oil for the benefit of sustainable development in West Africa
Variable
Symbol
Coded factor levels
-1
0
+1
Extraction time (min)
X1
40
50
60
Solvent volume (ml)
X2
200
225
250
Sample weight (g)
X3
45