Nonparametric procedures for simultaneous identification of the minimum effective dose in each of several groups

This paper considers the extension of the dose finding problem in a one-way layout setting to the case of several groups, in which the main goal is to identify the minimum effective dose (MED) of each group simultaneously. We propose two nonparametric procedures using the respective pairwise- and Helmert-type two-sample Mann-Whitney statistics, which are applied in a step-down testing scheme for identifying the MED simultaneously. The computation for the associated p-value of the identified MED vector is discussed. One numerical example is given to illustrate the proposed procedures.