power.lwyy.test: Power calculations for one-sided two-sample test of LWYY...

In agpower: Recurrent Event Analysis Planning for Robust Andersen-Gill Model

Power calculations for one-sided two-sample test of LWYY model parameter.

Description

Function to compute power at one-sided Type I control level alp/2 or determine parameters to target given power to test the hypotheses H0: RR = 1 vs HA: RR < 1 for the LWYY (Andersen-Gill with robust standard errors) model.

Usage

power.lwyy.test(
  N = NULL,
  RR = NULL,
  bta1 = NULL,
  thta,
  L = NULL,
  tau = NULL,
  lam = NULL,
  alp = 0.05,
  pow = NULL,
  ar = 0.5,
  frailty.type = c("unblind", "blind"),
  lam.type = c("base", "pool")
)

Arguments

N	Sample size.
RR, bta1	Rate ratio, log-transform of rate ratio. Provide at most one of RR and bta1.
thta	Variance of frailty parameter.
L	Number of events.
tau	Expected follow-up time.
lam	Event rate. If lam.type = "base", it is the event rate for control. If lam.type = "pool", it is the pooled rate.
alp	Two-sided alpha-level.
pow	Target power.
ar	Allocation ratio (Number control / Total)
frailty.type	Indicates whether frailty variance is based on blinded information ("blind") or unblinded ("unblind"). Default "unblind".
lam.type	Indicates whether event rate is based on control rate ("base") or pooled rate ("pool"). Ignored if lam = NULL. Default "base".

Details

An object of class "power.lwyytest" has the following components:

• method: Description of the test.

• N: Total sample size. N = Nc + Nt, where Nc = ar * N is the number on control and Nt = (1-ar) * N is the number on treatment.

• RR, RRCV: Rate ratio powered for and critical value for rate ratio.

• bta1, bta1CV: The log of RR, RRCV.

• thta: The variance of the frailty parameter.

• thtap: If frailty.type = "blind", the input variance from a blinded source.

• L: Number of events. Note that all else being equal, an increase (decrease) in N requires a decrease (increase) in L.

• tau, lam0: The mean follow-up time and control event rate. Note if tau = 1, then lam0 may be interpreted as mean cumulative intensity on control.

• lamp: If lam.type = "pool" and argument lam is not null, the input rate from a blinded source.

• alp: alp/2 is the one-sided Type I control level of the test H0: RR = 1 vs HA: RR < 1.

• pow: Power of the test.

• ar: Allocation to control ratio Nc/N.

• note: Set of key notes about the assessment.

Value

An object of class "power.lwyytest", a list of arguments, including those computed, with method and note elements.

Examples

x = power.lwyy.test(N = 1000, RR = 0.8, thta = 1, L = 1000, tau = 0.9, alp = 0.05, ar = 0.5)
print(x)

x = power.lwyy.test(N = 1000, RR = 0.8, thta = 1, tau = 0.9, lam = 1.23, alp = 0.05, ar = 0.5)
print(x)

x = power.lwyy.test(N = 1000, RR = 0.8, thta = 1, tau = NULL, lam = 1.23, alp = 0.05, ar = 0.5)
print(x, digits = 3)

agpower documentation built on June 8, 2025, 2 p.m.