I am designing an experiment to characterize a manufacturing process over a limited range of process parameters. There are two independent variables and one dependent variable. X1 ranges from 1 to 14 and X2 ranges from 1000 to 2000. Are there any free software packages I can download that will help me choose parameters for my experimetal matrix? Or could someone refer me to a textbook or website that would assist in experimental design? I would like to limit the number of parameters I consider to 10-15 (the number of experiments is limited by the amount of material I currently have). Thanks for any help you can offer!