TY - JOUR TI - On the optimality of orthogonal and balanced arrays with N≡ 0 (mod 9) runs AU - Chasiotis, V. AU - Chatzopoulos, S.A. AU - Kounias, S. AU - Farmakis, N. JO - Statistical Papers PY - 2021 VL - 62 TODO - 4 SP - 1965-1980 PB - Springer Science and Business Media Deutschland GmbH SN - 0932-5026 TODO - 10.1007/s00362-020-01167-3 TODO - null TODO - We investigate the role of orthogonal arrays (OAs) and balanced arrays (BAs) in both full and fractional factorial designs with N runs and m three-level quantitative factors. Firstly, due to the non-existence of the OA(18, 8, 3, 2), we find and construct a BA(18, 8, 3, 2) that represents the E-, A-, D-optimal design with N= 18 runs and m= 8 three-level factors under the main-effect model. Also, we are interested in comparing the OA(N, m, 3, 2)s with the BA(N, m, 3, 2)s, when they represent designs with N≡ 0 (mod 9) runs and m three-level factors with respect to the E-, A-, D-criteria under the second-order model. We provide a generalized definition of balanced arrays. Moreover, we find and construct the OA(N, m, 3, 2)s and the BA(N, m, 3, 2)s that represent the E-, A-, D-optimal designs with N= 9 , 18, 27, 36 runs and m= 2 three-level factors under the second-order model. Furthermore, it is shown that the BA(18, m, 3, 2)s, m= 3 , 4 and a BA(27, 3, 3, 2) perform better than the OA(18, m, 3, 2)s, m= 3 , 4 and the OA(27, 3, 3, 3), respectively, when they represent the corresponding designs with respect to the E-, A-, D-criteria under the second-order model. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature. ER -