2001 Volume 31 Issue 2 Pages 153-174
We consider the unbalanced one-way layout for comparing 3 treatment effects which can be assumed to satisfy the simple ordering μ1 ≤ μ2 ≤ μ3. This problem arises often in the comparison of three dose levels in medical trials, for example. The one-sided studentised range test provides a set of simultaneous confidence intervals for the ordered pairwise differences μj - μi, i < j which are one-sided and have infinite upper bounds. The new confidence interval procedure proposed in this article maintains the sensitivity of the one-sided studentised range test in detecting each of the ordered differences μj - μi > 0 while at the same time providing two-sided finite confidence intervals. Consequently, this new procedure has the advantage of allowing the same directional inferences as the one-sided studentised range test while additionally providing upper bounds on the differences among the treatment effects.
