Wei Liu
Department of Statistics
University of Central Florida
Multiple Comparison For Successive Means
Suppose that the k treatments under comparison are ordered in a certain way.
For example, they may be a sequence of increasing dose levels of a drug. It
is interesting to look directly at the successive differences between the
treatment effects mu_i , namely the set of differences mu_2
-mu_1,mu_3-mu_2. . . ,mu_k - mu_k-1. In particular,
directional inferences on whether mu_i < mu_i+1 or mu_i > mu_i+1 for i=1,2,. .
.,k-1 are useful. Lee and Spurrier
(1995) present a one-sided and a two-sided confidence interval procedures
for making successive comparisons between treatments. In this paper we
develop a new procedure which is sharper than both the one-sided and
two-sided procedures of Lee and Spurrier in terms of directional inferences.
This new procedure is able to make more directional inferences than the
two-sided procedure and maintains the inferential sensitivity of the
one-sided procedure. The critical point of the new procedure is the same as
that of Lee and Spurrier's one-sided procedure. We also propose a power
function for the new procedure and determine the sample size necessary for a
guaranteed power level. The application of the procedure is illustrated with
an example.)
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