![]() ![]() The second interim is primarily for efficacy.There is no desire to stop for efficacy, so the extreme effect sizeĪnd p-value required to cross the bound is considered appropriate.An earlier interim might be too soon to stop for a meaningful safety.There is no desire to stop this early for lack of a positive.There is an early look intended primarily for futility.These deserve careful attentionįor every trial and tend to be somewhat customized to be fit-for-purposeĪccording to all those involved in designing the trial. (1986) basic power calculation to compute sample size along theĮnrollment rates are fixed and enrollment duration is allowed to vary toĮnroll a sufficient sample size to power a study.Īll the parameters above are used. This methodįixes the duration of a study and varies enrollment rates to power a Sample size method and extend it to group sequential design. GsSurv() for examples with a stratified population or Stratum and exponential failure and dropout rates see the help file for We only use the simplest options here with a single Users may also be interested in the Shiny interface as a Hazards model with piecewise constant enrollment, piecewise exponentialįailure and dropout rates. With the flexibility allowed by the Lachin andįoulkes (1986) method for sample size under a proportional This article/vignette provides a basic time-to-event endpoint designsįor fixed designs using nSurv() and group sequentialĭesigns using gsSurv(). ![]()
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