The Selection of Terms in Response-Surface Models—How Strong is the Weak-Heredity Principle?

Abstract Model selection under the weak-heredity principle allows models that contain compound terms such as x 1 x 2 to have only one of the corresponding x 1 and x 2 terms In the model It is shown that the conditions required to justify use of the principle are so restrictive as to make It unusable in practice. An example is given to Illustrate this.