D-optimal chemical balance weighing designs with positively correlated errors: part III

In this paper we consider issues related to the determination of chemical balance weighing designs satisfying the criterion of D-optimality. This problem is considered under the assumption that the measurements are equally positively correlated and they have the same variances. We answer the question of how to add four runs to a regular D-optimal chemical balance weighing design in order to obtain a highly D-efficient design. The problem formulated in this way leads to an extension of results contained in a previous paper in Biometrical Letters.