This paper is intended to provide the reader with an introduction to ranked set sampling, a statistical technique for data collection that generally leads to more efficient estimators than competitors based on simple random samples. Methods for obtaining ranked set samples are described, and the structural differences between ranked set samples and simple random samples are discussed. Properties of the sample mean associated with a balanced ranked set sample are developed. A nonparametric ranked set sample estimator of the distribution function is discussed and properties of a ranked set sample analog of the Mann–Whitney–Wilcoxon statistic are presented.
Douglas A. Wolfe. "Ranked Set Sampling: An Approach to More Efficient Data Collection." Statist. Sci. 19 (4) 636 - 643, November 2004. https://doi.org/10.1214/088342304000000369