Consider the experimental design problem in which there are three factors: (1) impeller speed (in rpm) with associated variable , such that the lower and upper levels are 250 and 400, respectively, (2) amount of binding solution (in %) with associated variable , such that the lower and upper levels are 60 and 70, respectively, (3) pelletization time (in min) with associated variable , such that the lower and upper levels are 5 and 20, respectively.