Robust multiple comparisons against a control group with application in toxicology
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The Dunnett procedure compares several treatment or dose groups with a control group, while controlling the familywise error rate. When deviations from the normal distribution and heterogeneous variances occur, the nominal α level may be violated, and power may be reduced. Various robust modifications are discussed, whereby the novel most likely transformation (MLT)-Dunnett version is recommended as almost always appropriate by means of a simulation study. The MLT-Dunnett is especially useful because it can jointly and comparably analyse differently scaled endpoints. Furthermore, a related multiple endpoints test is proposed using the odds ratio as a common effect size. With the statistical software R, the method is readily applicable using the CRAN libraries |multcomp| and |mlt|, real data can be easily analyzed.
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