Adaptive group sequential confidence intervals for the ratio of normal means
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Date
2009-02-02T10:41:10Z
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Abstract
In controlled group sequential trials, we consider the ratio of normal means as the
effect measure of interest and derive group sequential nested confidence intervals
on this parameter.
In an interim analysis, the sample sizes of the following stages can be determined
in a completely adaptive way using the unblinded data from all previously performed stages.
Despite the data-dependent adaptation, the nested confidence intervals always keep the predefined
confidence coefficient.
Using nested confidence intervals, we make test decisions either in noninferiority or in superiority trials.
However, in an interim analysis, we can change the planning from showing noninferiority to showing superiority
or vice versa without affecting the predefined confidence coefficient of the nested intervals.
A real data example is worked out in detail and the change in the planning from showing superiority to showing
noninferiority is shown during the ongoing trial.
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Keywords
adaptive sample size planning, group sequential clinical trials, ratio of means, switching between noninferiority and superiority