mixed.eff.params {clusterPower} | R Documentation |
This function is designed to calculate the overall variance for cluster-level outcomes in a mixedeffect Poisson model. Conditional expectation calculations are implemented.
mixed.eff.params(pi0, btw.clust.var, Tk)
pi0 |
the baseline cluster-level mean on the scale of the link function |
btw.clust.var |
the between-cluster-variance |
Tk |
the at-risk time for each cluster |
The mixed.eff.params()
function is used by the hayes.power.poisson()
function to
compute the effective coefficient of variation, or k, for a particular
study design.
A numeric vector with the following three named elements, in order: ["expectation"] the overall mean of cluster-level outcomes, ["variance"] the overall variance of cluster-level outcomes, ["hayes.k"] the estimated coefficient of variation.
Nicholas G. Reich
Reich NG et al. PLoS ONE. Empirical Power and Sample Size Calculations for Cluster-Randomized and Cluster-Randomized Crossover Studies. 2012. http://ow.ly/fEn39
Hayes RJ and Bennett S. Int J Epi. Simple sample size calculation for cluster-randomized trials. 1999. http://www.ncbi.nlm.nih.gov/pubmed/10342698
mixed.eff.params(pi0=log(1), btw.clust.var=.5, Tk=100)