Abstract: With reference to an s m factorial, this paper shows that for 0<u<=st+1, if any u runs are added to an s-symbol orthogonal array of strength 2t then the resulting plan is E-optimal of resolution 2t+1 within the class of plans involving the same number of runs. This result has been partially extended to asymmetric factorials and utilized in proving the E-optimality of certain other plans which are nearly saturated and not derivable by augmenting orthogonal arrays.
Key words and phrases: Difference matrix, E-optimality, Kronecker sum, orthogonal array, nearly saturated plans, resolution.