Why DF of pure error of LOF test change when terms are added or removed from the model?
Hi JMPers, I was modeling with fractional factorial design 2(7-4) with 3 center points.When I change the terms in the model, DF of pure error in the LOF test also changes. (10 to 14) In Minitab it doesn't change with the change of the model (same DF = 2 for 3 replicates of center points). I think that DF of pure error is calculated from the number of pure replication ...
steve_reinhart
dale_lehman