Abstract
Group sequential designs are widely used in Phase II clinical trials, which are usually undertaken to evaluate the response probability of specific treatment regimen. In most randomized clinical trials with sequential patient entry, fixed sample size design is unjustified on ethical grounds and sequential designs are often impractical. However group sequential designs are generally more practical and they provide much of the saving possible from sequential designs. Optimal restricted two-stage design is the simplest form of a group sequential design. In this study, group sequential design obtained by α*(t) functions characterized using the type-I error probability and optimal restricted two stage design has been compared for the cases that the group sizes are equal. Furthermore, their efficiency regarding fixed sample size design has been calculated and the results have been discussed.
Highlights
Scientific and economic reasons, clinical trials are often repeatedly monitored for evidence of treatment benefit or harm.To achieve this, statisticians conduct interim analyses periodically on accumulating data [1]
Optimal restricted two-stage design is the simplest form of a group sequential design
Jennison [7] and Eales&Jennison [8] explored the extent of possible reductions in expected sample size by searching for optimal symmetric group sequential one-sided tests
Summary
Scientific and economic reasons, clinical trials are often repeatedly monitored for evidence of treatment benefit or harm.To achieve this, statisticians conduct interim analyses periodically on accumulating data [1]. DeMets&Ware [5, 6] considered asymmetric group sequential boundaries adapted from Pocock and O’Brien&Fleming designs and from Wald’s sequential probability ratio test. These designs are based on spaced analyses. Lan&DeMets [13], Kim&DeMets [14] proposed the group sequential design obtained by α∗ (t), use function, which characterizes spending the type I error probability (α) This design is more useful because it is not necessary that each group has equal observation. Dewith [18] extended the work of Calton and McPherson for binomial responses by developing optimal designs that allowed acceptance or rejection at the first stage none of these designs used the fixed sample critical value at the final stage. We compared the statistical properties of the group sequential design based on α∗ (t) function, and optimal restricted two-stage design in the setting of onesided comparative clinical trials with normal response
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