npordtests: An R Package of Nonparametric Tests for Equality of Location Against Ordered Alternatives

Ordered alternatives are an important statistical problem in many situation such as increased risk of congenital malformation caused by excessive alcohol consumption during pregnancy life test experiments, drug-screening studies, dose-finding studies, the dose-response studies, age-related response. There are numerous other examples of this nature. In this paper, we present the npordtests package to test the equality of locations for ordered alternatives. The package includes the JonckheereTerpstra, Beier and Buning's Adaptive, Modified Jonckheere-Terpstra, Terpstra-Magel, FerdhianaTerpstra-Magel, KTP, S and Gaur's Gc tests. A simulation study is conducted to determine which test is the most appropriate test for which scenario and to suggest it to the researchers.