- Sampling variogram
In mathematical

statistics , a**sampling variogram**is a graph that shows where a significant degree of causality (in this context,spatial dependence in sample spaces or sampling units) dissipates into randomness. A sampling variogram is obtained by plotting statisticallly significant variance terms of a temporally or "in situ" ordered set of measured values against the variance of the set and the lower limits of its asymmetric 95% and 99% confidence ranges. Corrected sampling variograms derive from uncorrected ones when extraneous measurement variances are subtracted before spatial dependence is verified. Bre-X's bogus gold grades for crushed, salted and "in situ" ordered core samples of Borehole BSSE198 in Busang's South-East zone give the following uncorrected sampling variogram.

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*http://www.geostatscam.com/corrected_sampling_variogram.htm The corrected sampling variogram for Bre-X's bonanza borehole, its primary data set and test statistics are posted on this page.*] A temporally ordered set of on-stream data for mill feed to a mineral processing plant, its test statistics and sampling variogram are given in [*http://www.geostatscam.com/Excel/Appendix%20D.xls Appendix D*] of "Sampling in Mineral Processing". Avariogram or a semi-variogram, unlike the above sampling variogram, does not show where spatial dependence in sample spaces dissipates into randomness because kriging variances of sets of kriged estimates are invalid measures for variability, precision and risk.**References**# Armstrong, M and Champigny, N, 1988, A Study on Kriging Small Blocks, CIM Bulletin, Vol 82, No 923

# Clark, I, 1979, Practical Geostatistics, Applied Science Publishers, London

# David, M, 1977, Geostatistical Ore Reserve Estimation, Elsevier Scientific Publishing Company, Amsterdam

# Hald, A, 1952, Statistical Theory with Engineering Applications, John Wiley & Sons, New York

# ISO/DIS 11648, Statistical aspects of sampling from bulk materials, Part 1: General Principles

# Journel, A G and Huijbregts, C J, 1978, Mining Geostatistics, Academic Press Inc, London 1978

# Philip, G M and Watson, D F, 1986, Matheronian Geostatistics; Quo Vadis?, Mathematical Geology, Vol 18, No 1**External links*** [

*http://www.geostatscam.com This website explains how to design uncorrected and corrected sampling variograms, and how to verify where spatial dependence in sample spaces or sampling units dissipates into randomness*]

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