sampleLogrankStoppingTimes {safestats}

Simulate stopping times for the exact safe logrank test

Description

Simulate stopping times for the exact safe logrank test

Usage

sampleLogrankStoppingTimes(
  hazardRatio,
  alpha = 0.05,
  alternative = c("twoSided", "less", "greater"),
  m0 = 50000L,
  m1 = 50000L,
  nSim = 1000L,
  groupSizePerTimeFunction = returnOne,
  parameter = NULL,
  nMax = Inf,
  pb = TRUE
)

Arguments

hazardRatio

numeric that defines the data generating hazard ratio with which data are sampled.

alpha

numeric in (0, 1) that specifies the tolerable type I error control –independent on n– that the designed test has to adhere to. Note that it also defines the rejection rule e10 > 1/alpha.

alternative

a character string specifying the alternative hypothesis, which must be one of "twoSided" (default),"greater" or "less". The alternative is pitted against the null hypothesis of equality of the survival distributions. More specifically, let lambda1 be the hazard rate of group 1 (i.e., placebo), and lambda2 the hazard ratio of group 2 (i.e., treatment), then the null hypothesis states that the hazard ratio theta = lambda2/lambda1 = 1. If alternative = "less", the null hypothesis is compared to theta < 1, thus, lambda2 < lambda1, that is, the hazard of group 2 (i.e., treatment) is less than that of group 1 (i.e., placebo), hence, the treatment is beneficial. If alternative = "greater", then the null hypothesis is compared to theta > 1, thus, lambda2 > lambda1, hence, harm.

m0

Number of subjects in the control group 0/1 at the beginning of the trial, i.e., nPlan[1].

m1

Number of subjects in the treatment group 1/2 at the beginning of the trial, i.e., nPlan[2].

nSim

integer > 0, the number of simulations needed to compute power or the number of events for the exact safe logrank test under continuous monitoring

groupSizePerTimeFunction

A function without parameters and integer output. This function provides the number of events at each time step. For instance, if rpois(1, 7) leads to a random number of events at each time step.

parameter

Numeric > 0, represents the safe tests defining thetaS. Default NULL so it's decided by the algorithm, typically, this equals hrMin, which corresponds to the GROW choice.

nMax

An integer. Once nEvents hits nMax the experiment terminates, if it didn't stop due to threshold crossing crossing already. Default set to Inf.

pb

logical, if TRUE, then show progress bar.

Value

a list with stoppingTimes and breakVector. Entries of breakVector are 0, 1. A 1 represents stopping due to exceeding nMax, and 0 due to 1/alpha threshold crossing, or running out of participants, which implies that the corresponding stopping time is Inf.

Author(s)

Muriel Felipe Perez-Ortiz and Alexander Ly

Examples

sampleLogrankStoppingTimes(0.7, nSim=10)