Stratified Median Ranked Set Sampling:Optimum and Proportional Allocations

In this paper، for the Stratified Median Ranked Set Sampling (SMRSS)، proposed by Ibrahim et al. (2010)، we examine the proportional and optimum sample allocations that are two well-known methods for sample allocation in stratified sampling. We show that the variances of the mean estimators of a symmetric population in SMRSS using optimum and proportional allocations to strata are smaller than the corresponding variances in Stratified Random Sampling (STRS). It is also shown that for a fixed value of sampling cost in strata، the variance of mean estimator with optimum allocation is less than or equal to the variance of mean estimator with proportional allocation in SMRSS. In addition، we develop the results obtained by Ibrahim et al. (2010) for proportional allocation in SMRSS for some symmetric and non-symmetric distributions when the parameters of distributions are varying.