Standardized mean differences in adaptive group sequential trials
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Date
2009-02-02T10:42:55Z
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Abstract
For studies comparing two independent groups, experimental E and control C, with normally distributed
response variables, the outcome measure standardized differences of means is considered that is scale and
translation invariant.
This effect measure enables a convenient specification of a noninferiority margin in a concrete application.
The present paper provides in particular a group sequential confidence interval approach to noninferiority trials
and to switching between noninferiority and superiority for the effect size measure standardized mean difference.
During the course of the trial, the sample size can be calculated in a completely adaptive way, based on the
unblinded data of previously performed stages.
Concrete rules for sample size updating are provided in this paper.
Moreover, in each interim analysis, it is possible to change the planning from showing noninferiority to showing
superiority or vice versa.
A real data example is worked out in detail and the change in the planning from showing noninferiority to showing
superiority is considered during the ongoing trial.
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Keywords
adaptive sample size planning, effect size, multi-stage confidence intervals, standardized difference of means, switching between noninferiority and superiority