Sampling using ranked sets: Concepts, results and perspectives

Traditionally we have used the simple random sampling to select samples. Most of the models of the statistic are supported by the use of samples selected by means of this design. During the last decade it has begun to be used an alternative design that shows an improvement, in some cases, with respect to the sampling error and the accuracy. It is called Ranked Set Sampling. A random selection is made with the replacement of samples, which are ordered (ranked). Each order statistic is observed once. This process can be repeated or not. In this paper a review of the most significant results in this theme is made and some open problems related with this sampling design that should be studied are settled down.