A Study of Variance Estimators for Material Sampling Using Computerized Models of Contaminant Heterogeneity in Soil Stockpiles.

During the sampling of contaminated soil, sampling errors are unavoidable becauseof the spatial heterogeneity of the contaminant distribution. The variance is a convenientindicator for the potential magnitude of these errors. Four variance estimators are constructedfor use in material sampling, all of which take account of the heterogeneity and the samplingdesign. Based on large scale three-dimensional computerized models of contaminantheterogeneity in soil stockpiles, these variance estimators are compared using a Monte Carlosimulation of different sampling designs. The Mean Squared Error (MSE) of each varianceestimator is used to assess (and compare) the performance of each variance estimator: the lowerthe mean square error, the better its performance.