power.surv.test: Power and sample size for survival distribution (One-sample)

In statapps/power.ctepd: Power and sample size for clinical trials and epidemiology

Power and sample size for survival distribution (One-sample)

Description

Compute power and sample size of test or determine distribution of alternative hypothesis to obtain target power (same as power.anova.test).

Usage

power.surv.test(n = NULL, sig.level = 0.05, s0 = NULL, s1 = NULL, 
                year = 3, accrual = 3, followup = 3, futile = NULL, 
                futile.prob = 0.01, power = NULL, 
                tol = .Machine$double.eps^0.25)

Arguments

n	Number of observations
sig.level	Significance level (Type I error probability)
year	Time point in which survival function is evaluated
s0	Survival function at yaer = year under H0
s1	Survival function at yaer = year under H1
accrual	Years of accrual
followup	Years of followup
power	Power of test (1 minus Type II error probability)
futile	Optinal futility analysis, define the percentage of pearson-year for futility analysis. Value shall be between 0 and 1. Default is NULL.
futile.prob	Significant level of futility analysis. Probability of rejecting the alternative hypothesis when H1 is true. Default is 0.01
tol	tol for uniroot function

Details

These calculations use Poisson process and person-year under exponentioal distribution.

Exactly one of the parameters 'n','power' and 's1' must be passed as NULL, and that parameter is determined from the others. Notice that the last one has non-NULL default so NULL must be explicitly passed if you want to compute it.

Value

Object of class 'power.htest', a list of the arguments (including the computed one) augmented with 'method' and 'note' elements.

person.year	Total person-year of followup required for the final analysis
median.dur	Median duration of followup
crtl.event	Critical value for number of observed events to reject the null hypothesis H0
crtl.survf	Critical value for observed survival function at year = year to reject the null hypothesis H0
futile.pyear	Person-year for interim futility analysis
futile.event	Reject H1 if observed event > futile.event
futile.prob	Probability of rejection H1 in the interim analysis when H1 is true

Note

'uniroot' is used to solve power equation for unknowns, so you may see errors from it, notably about inability to bracket the root when invalid arguments are given.

Author(s)

Bingshu E. Chen ([e-mail])

References

Lawless, J. Statistical Models and Methods for Lifetime Data, John Wiley and Sons, 1982 (equation 3.2.7 (page 108).

See Also

power.t.test, power.2surv.test, pwr.p.test

Examples

##
#pw = power.surv.test(n = 75, s0 = 0.83, s1 = 0.92, sig.level = 0.1)
#pw = power.surv.test(n = 75, s0 = 0.83, power = 0.8, followup = 3.08, sig.level = 0.1)

pw = power.surv.test(power = 0.8, s0 = 0.83, s1 = 0.92, followup = 3, sig.level = 0.1)
print(pw, digits = 4)

statapps/power.ctepd documentation built on April 26, 2024, 3:22 a.m.