Partially sequential nonparametric two-"sample test for ordered categorical'data

Abstract

In multi-sample inference problems, in particular two-sample inference problems, a partially sequential scheme, introduced by Wolfe (1977), is instrumental in reducing time and/or cost of the experiment when one sample is very difficult to obtain and/or costly compared to the other one. The present paper deals with a partially sequential test procedure for ordered categorical data. "Ridit", introduced by Bross (1958) and based on a fixed number of observations drawn from the first population, is used to provide a suitable stopping rule. A random number of observations are drawn from the second population using that stopping rule. A suitable test statistic is suggested based on those fixed number of observations from the first population and a random number of observations from the second population. Various asymptotic properties of the test procedure are explored. The paper concludes with the results of a simulation study.