Boundary derivation for binding or non-binding futility stopping only.

gsLowerCRT is used to calculate the stopping boundaries for a group sequential trial with 1 or 2-sided futility-only stopping. Code adapted from gsDesign package.

Usage

gsLowerCRT(
  theta = 0,
  I,
  falseneg,
  b = NULL,
  sides = 1,
  binding = TRUE,
  tol = 1e-06,
  r = 18,
  printerr = 0
)

Arguments

theta

Effect size under null hypothesis. Default value is 0.

I

Information levels at interim analyses for which stopping boundaries are calculated. At any given interim analysis this should include the information levels at the current and previous analyses.

falseneg

Type II error spent for the interim analyses at the information levels specified by I.

b

Upper efficacy boundary values for the interim analyses at the information levels specified by I.

sides

1= 1-sided test (default)
2= 2-sided test

binding

TRUE= binding (default)
FALSE= non-binding

tol

Tolerance for error (default is 0.000001). Normally this will not be changed by the user. This does not translate directly to number of digits of accuracy, so use extra decimal places.

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.

printerr

Print output for debugging.

Value

Object containing the following elements:

k

Number of interim analyses.

theta

As input.

I

As input.

a

Computed lower futility boundaries at the specified interim analyses.

b

As input.

r

As input.

error

error flag returned; 0 if convergence; 1 indicates error.

References

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

Author

Lee Ding lee_ding@g.harvard.edu