Survival tests for r groups

Abstract

In this paper we give the generalization of the score tests covering the case of ties and we give examples where the expressions in matrix form are completely specified for the weighted tests and the score tests for the case of r groups. It is worth mentioning that although the score tests are not generally included in the commercial software, these tests should be used if it can be assumed that the censoring mechanism is equal in the r groups or if there is no censoring (Lawless, 1982). We establish the equivalence between "numerators" of these families of tests. As result of this equivalence we define four new tests that complete the classification of score and weighted tests. The Kruskal-Wallis test (1952) appears as a particular case of the score tests for the case of non-censoring. A simulation study has been done in order to compare the performance of the tests described in this paper. An example is included to make the understanding of the paper easier.