VarClosed_Li {SteppedPower}

Closed formula for treatment variance, with proportional decay

Description

From Li et al "Design and analysis considerations for cohort stepped wedge cluster randomized trials with a decay correlation structure"

Usage

VarClosed_Li(trtMat, tau, psi, N, AR)

Arguments

trtMat

a matrix trtMat to define treatment allocation, where rows and columns correspond to cluster and timepoints, respectively

tau

numeric, standard deviation of random intercepts

psi

numeric, random subject specific intercept.

N

numeric, number of individuals per cluster.

AR

numeric (scalar), It defines the AR(1)-correlation of random effects.

Value

numeric, variance of the estimator for treatment effect

Examples

##  test setting, from Hussey&Hughes 2007  ####
trtMat <- construct_DesMat(c(6,6,6,6))$trtMat
tau <- .025 ; N <- 100 ; psi <- .1 ; AR <- .6
tmp <- VarClosed_Li(trtMat, tau=tau, psi=psi, N=N, AR=AR)
tTestPwr((.05-.032), se=sqrt(tmp), Inf)
glsPower(Cl=rep(6,4), mu0=.05, mu1=.032, AR=AR,
         tau=tau, N=N, sigma=0, psi=psi, verbose=0)