Compute stopping boundary crossing probabilities.

Usage

gsProbabilityCRT(theta = 0, I = 1, a = 0, b = 1, sides = 1, r = 18)

theta: Effect size. Default value is 0.
I: Information levels at interim analyses for which boundary crossing probabilities are computed.
a: Lower futility boundaries for the interim analyses at the information levels specified by I.
b: Upper efficacy boundaries for the interim analyses at the information levels specified by I.
sides: 1= 1-sided test (default)
2= 2-sided test.
r: Integer value controlling grid for numerical integration as in Jennison and Turnbull (2000); default is 18, range is 1 to 80. Larger values provide larger number of grid points and greater accuracy. Normally r will not be changed by the user.

Object containing the following elements:

k: Number of interim analyses.
theta: As input.
I: As input.
lower: List containing the lower futility boundaries (bound) and the corresponding probabilities of crossing the lower boundaries given theta (prob).
upper: List containing the upper efficacy boundaries (bound) and the corresponding probabilities of crossing the upper boundaries given theta (prob).
power: Estimated power for trial.
futile: Estimated probability of futility for trial
r: As input.

Jennison C and Turnbull BW (2000), Group Sequential Methods with Applications to Clinical Trials. Boca Raton: Chapman and Hall.