COUPLED SAMPLES IN SIMULATION

Assume that we wish to generate two samples of n independent identically distributed random variables, (XI, ..., X.) and (y" ..., Y.), where XI and YI have densitiesfand g, respectively. If these samples are used in a simulation, andf is close to g, it is sometimes desirable to have close simulation results. This can be achieved by insisting that both samples agree in most of their components, that is, Xi = Yi for as many i as possible under the given distributional constraints. Samples with this property are said to be optimally coupled. In this paper, we propose and study various methods of coupling two samples, a sequence of samples and an infinite family of samples.