Step-down trend tests for identifying the minimum effective dose.
Many authors, most recently Tamhane, Hochberg, and Dunnett (18), have studied the problem of determining the minimum effective dose in dose-response studies. Based on past research and on findings from their own extensive simulation study, which covered a wide range of balanced normal homoscedastic situations, Tamhane et al. recommended a procedure they called SD2L, since it exhibited good performance in almost all the situations they studied. This method is a step-down procedure with a simple linear contrast-based trend test at each step. In this paper, we demonstrate that replacing the linear contrast trend test by Bartholomew's test leads to a procedure, SD2B, that consistently outperforms SD2L. In addition to the balanced normal homoscedastic framework, the finite sample performance of these procedures is also explored under unbalanced and/or heteroscedastic conditions. A third procedure, SD2W, which replaces the linear contrast test by Welch's test, offers some improvement over SD2B in a few heteroscedastic situations. In many cases, the increase in efficiency of SD2B and SD2W over SD2L exceeds 10%.
Amaratunga
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Department of Preclinical Biostatistics, R.W. Johnson Pharmaceutical Research Institute, Raritan, New Jersey 08869-0602, USA.
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D000818:Animals; D001702:Biopharmaceutics / Q000706:statistics & numerical data*; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D004305:Dose-Response Relationship, Drug; D004715:Endometriosis / Q000188:drug therapy; D005260:Female; D016014:Linear Models; D011817:Rabbits; D011897:Random Allocation; D012107:Research Design