Estimators for the Parameter Mean of Morgenstern Type Bivariate   Generalized Exponential Distribution Using Ranked Set Sampling
  In situations where the sampling units in a study can be more easily ranked based on the measurement of an auxiliary variable, ranked set sampling provide unbiased estimators for the mean of a population that they are more efficient than unbiased estimator based on simple random sample. In this paper, we consider the Morgenstern type bivariate generalized exponential distribution (MTBGED) and obtain several unbiased estimators for a parameter mean of the marginal distribution of MTBGED based on different ranked set sampling schemes. The efficiency of all considered estimators are evaluate and has also been demonstrated with numerical illustrations. 
Saeid Tahmasebi and Ali Akbar Jafari
math.ST stat.TH