CONSTRUCTING ORTHOGONAL FRACTIONAL FACTORIAL-DESIGNS WHEN SOME FACTOR-LEVEL COMBINATIONS ARE DEBARRED

In a factorial experiment, certain combinations of factor levels may n ot be feasible in the sense that observations are not available under such combinations. If an orthogonal fractional factorial design contai ns such infeasible combinations, there will be missing data, and it ma y not be possible to augment the design without losing the property of orthogonality. Sometimes certain combinations may be operationally fe asible, but they are ruled out for other reasons. This article studies the construction of orthogonal designs excluding such combinations. A modification of Franklin and Bailey's algorithm for selecting definin g contrasts, which takes debarred combinations into account, is also p resented.