Response Surface Methodology (RSM) is a collection of mathematical and statistical techniques useful for analyzing
experiments where the yield is believed to be influenced by one or more controllable factors. Box and Hunter (1957) introduced
rotatable designs in order to explore the response surfaces. The analogue of Box-Hunter rotatability criterion is a requirement
that the variance of i
yˆ(x)/ x be constant on circles (v=2), spheres (v=3) or hyperspheres (v 4) at the design origin.