ciapower: Power of Interaction Test for Exponential Survival

Description Usage Arguments Value Side Effects AUTHOR References See Also Examples

Description

Uses the method of Peterson and George to compute the power of an interaction test in a 2 x 2 setup in which all 4 distributions are exponential. This will be the same as the power of the Cox model test if assumptions hold. The test is 2-tailed. The duration of accrual is specified (constant accrual is assumed), as is the minimum follow-up time. The maximum follow-up time is then accrual + tmin. Treatment allocation is assumed to be 1:1.

Usage

1
2
ciapower(tref, n1, n2, m1c, m2c, r1, r2, accrual, tmin, 
         alpha=0.05, pr=TRUE)

Arguments

tref

time at which mortalities estimated

n1

total sample size, stratum 1

n2

total sample size, stratum 2

m1c

tref-year mortality, stratum 1 control

m2c

tref-year mortality, stratum 2 control

r1

% reduction in m1c by intervention, stratum 1

r2

% reduction in m2c by intervention, stratum 2

accrual

duration of accrual period

tmin

minimum follow-up time

alpha

type I error probability

pr

set to FALSE to suppress printing of details

Value

power

Side Effects

prints

AUTHOR

Frank Harrell

Department of Biostatistics

Vanderbilt University

f.harrell@vanderbilt.edu

References

Peterson B, George SL: Controlled Clinical Trials 14:511–522; 1993.

See Also

cpower, spower

Examples

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
# Find the power of a race x treatment test.  25% of patients will
# be non-white and the total sample size is 14000.  
# Accrual is for 1.5 years and minimum follow-up is 5y.
# Reduction in 5-year mortality is 15% for whites, 0% or -5% for
# non-whites.  5-year mortality for control subjects if assumed to
# be 0.18 for whites, 0.23 for non-whites.
n <- 14000
for(nonwhite.reduction in c(0,-5)) {
  cat("\n\n\n% Reduction in 5-year mortality for non-whites:",
      nonwhite.reduction, "\n\n")
  pow <- ciapower(5,  .75*n, .25*n,  .18, .23,  15, nonwhite.reduction,  
                  1.5, 5)
  cat("\n\nPower:",format(pow),"\n")
}


Search within the Hmisc package
Search all R packages, documentation and source code

Questions? Problems? Suggestions? or email at ian@mutexlabs.com.

Please suggest features or report bugs with the GitHub issue tracker.

All documentation is copyright its authors; we didn't write any of that.