You can used CCD. For that you can refer my papers

You can use central composite faced design CCFD. It have only of 3 levels and gives you a low max variance of prediction of the response. For the reduction of the model you can use first the t-student taste and then the extra sum of square test or minimice the rate R2/adjusted R2 with a computer program.

Sorry,...R2/adjustedR2 ratio must be closer to 1

hi,

I am interesting to optimize medium for enzyme production using Taguchi orthogonal array. I used Design expert software (dx7). finally i didnt get any F value but there is a column for it............. how to rectify it......... anyone can guide me