Either a number denoting the effective sample size or if x is of class
causalWeights, then returns a list of both values in the treatment
and control groups.
Arguments
x
Either a vector of weights summing to 1 or an object of class
causalWeights
Methods (by class)
ESS(numeric): default ESS method for numeric vectors
ESS(causalWeights): ESS method for objects of class causalWeights
Details
Calculates the effective sample size as described by Kish (1965).
However, this calculation has some problems and the PSIS()
function should be used instead.