  Design of experiment with related factors can be implemented by using the
technique of sliding levels. Taguchi (1987) proposed an analysis strategy by
re-centering and re-scaling the slid factors. Hamada and Wu (1995) showed via
counter examples that in many cases the interactions cannot be completely
eliminated by Taguchi's strategy. They proposed an alternative method in which
the slid factors are modeled by nested effects. In this work we show the
inadequacy of both methods when the objective is response prediction. We
propose an analysis method based on a response surface model, and demonstrate
its superiority for prediction. We also study the relationships between these
three modeling strategies.
