survival-design-routing

name	survival-design-routing
description	Choose the appropriate gsDesign survival or exact-binomial workflow when requests involve calendar-time interim analyses, event- or information-driven survival looks, seasonal rare-event exact-binomial monitoring, or explicit randomization ratios; covers when to use gsSurvCalendar(), gsSurv(), simBinomialSeasonalExact(), and toBinomialExact().

gsDesign survival design routing

• If a request specifies analyses by calendar dates or months from trial start or enrollment opening, use gsSurvCalendar(calendarTime = ...). Example: "add an interim analysis 24 months after enrollment opens" means include 24 in calendarTime.
• When changing only analysis timing, preserve the original design specifications unless the user asks to change them.
• Use gsSurv() when timing is event-driven or specified by information fractions rather than fixed calendar times.
• Very low planned event counts, such as fewer than 100 total events, can be a cue to discuss exact-binomial rare-event methods, but do not switch solely because counts are low.
• Use simBinomialSeasonalExact() and toBinomialExact() when the endpoint/workflow is seasonal rare-event exact-binomial monitoring; otherwise keep the appropriate survival design function.
• Set ratio explicitly when randomization is specified; ratio = 1 means equal experimental:control randomization.