Estimation of the parameters of Downtonʹs bivariate exponential distribution using ranked set sampling scheme

The parameters of Downtonʹs bivariate exponential distribution are estimated based on a ranked set sample. Parametric and nonparametric methods are considered. The suggested estimators are compared to the corresponding ones based on simple random sampling. It turns out that some of the suggested estimators are significantly more efficient than the ones based on simple random sampling.