Confounding revisited with commutative computational algebra

We use computational commutative algebra to discuss and compute confounding relations for general, e.g. non-regular, fractions of a factorial design. Our method is based on the algebraic description of the design as the set of solutions of a system of polynomial equations. Grobner bases of polynomial ideals are used as computational tools. Symbolic softwares are used to derive confounding relations as normal forms of the interaction terms with respect to a given term ordering. (C) 2002 Elsevier B.V. All rights reserved.