| PRIMEplus.SampleSize {PRIMEplus} | R Documentation |
Sample Size
Description
Compute the sample size for a given power
Usage
PRIMEplus.SampleSize(power=0.8, rand_ratio=0.5, effect_p=0.6, enroll_rate=380*0.25/6,
lambda1=0.117, HR=0.5, tau=12*5, t1=1, maxiter=100000, stopTol=1e-4,
alpha=0.05, num_rand=1000, nsim=10000, min.N=100, max.N=700,
tol.power=0.01, tol.N=1, print=1,
min.sample.size=50, min.n.event=5, min.per.trt=0.25)
Arguments
power |
The desired power. The default is 0.8. |
rand_ratio |
Allocation ratio |
effect_p |
Vector for proportion of responders in the treatment arm at baseline (see details) |
enroll_rate |
Enrollment rate in subjects per month |
lambda1 |
Baseline hazard in terms of months |
HR |
Vector of hazard ratios for responders against controls (see details) |
tau |
Total study duration |
t1 |
Delayed duration |
maxiter |
Maximum number of iterations in the EM algorithm. The default is 100000. |
stopTol |
Stopping tolerance in the EM algorithm. The default is 1e-4. |
alpha |
Significance level. The default is 0.05. |
num_rand |
Number of replications in the re-randomization test. The default is 1000. |
nsim |
Number of simulations in computing power (see Details). The default is 10000. |
min.N |
Lower bound for the sample size. The default is 100. |
max.N |
Upper bound for the sample size. The default is 700. |
tol.power |
Stopping tolerance for the power. The default is 0.01. |
tol.N |
Stopping tolerance for the sample size. The default is 1. |
print |
0 or 1 to print information. The default is 1. |
min.sample.size |
Minimum sample size. The default is 50. |
min.n.event |
Minimum number of events. The default is 5. |
min.per.trt |
Minimum proportion of controls and treated subjects. The default is 0.25. |
Details
The length and order of effect_p must be the same as HR. Both of these vectors
should contain information only for the groups of responders. For example, if there are
full responders and partial responders, then effect_p and HR would be vectors
of length two.
This uses a bisection method to estimate the sample size. At each iteration,
the estimated power power_est is computed using PRIMEplus.Power
for a given sample size holding all other parameters fixed.
The algorithm terminates when abs(power - power_est) <= tol.power or
when the length of the estimated interval containing the sample size is
less than or equal to tol.N.
NOTE:
It is important to note that the power for a given sample size is estimated by
running a simulation. Thus, by setting a different seed, a different result may
be returned. Therefore, to ensure a more precise estimated sample size, set the
option nsim to a large value and/or run this function several times by
setting different seeds and examine the distribution of returned sample sizes.
Value
A list containing the sample size and power.
Author(s)
Zhenzhen Xu <Zhenzhen.Xu@fda.hhs.gov>, Yongsoek Park <yongpark@pitt.edu> and Bin Zhu <bin.zhu@nih.gov>