If the sample size n is large enough, then the exact polynomial regression designs obtained by rounding the weights of the approximate D-optimal design to integral multiples of 1/n are D-optimal. This was shown by Salaevskiℝ3i and Gaffke. In this note, an efficient algorithm to determine the minimum sample size nd for a polynomial model of degree d is derived from a condition given by Huang. Under an additional assumption it is shown that the conditions of Gaffke and Huang are equivalent; the additional assumption for polynomial degree d•40 is verified.
