Saturated array
In a saturated array, a controllable factor is substituted for the by-product interactions. It is assumed that the additional factors are also not likely to interact with any of the other factors. Using a saturated array, a two-factor test matrix could be used to test three factors. Factor C, a controllable factor, replaces the by-product interaction A*B. Using the saturated array allows three factors to be tested in four tests rather than in eight, as would be required by a standard orthogonal array.