- Jan Visman
Jan Visman played a key role in building a bridge between sampling theory with its homogeneous
populationsand sampling practice with its heterogeneous sampling units and sample spaces. Born in Deventer, The Netherlands, on July 2, 1914, Visman studied mining engineering at the Technical University in Delft, and was employed at the Dutch State Mines during the Second World War.
He surfaced after the war with a massive amount of test results determined in samples selected from heterogeneous sampling units of coal. In fact, he had gathered so much valuable information that he was encouraged to write a
PhDthesis on the sampling of coal. Dr Jan Visman defended his PhD thesis titled "“De Monsterneming van Heterogene Binomiale Korrelmengsels, in het Bijzonder Steenkool”" at the Technical University of Delft on December 17, 1947.
Visman proved that the
varianceof the primary sample selection stage (the sampling variance) is the sum of the composition variance and the distribution variance. The composition variance is a measure for variabilitybetween particles within primary increments. The distribution variance, in contrast, is a measure for variability between primary increments in a sampling unit, and, thus, for its degree of heterogeneity. He described a simple experiment to estimate the composition and distribution components of the sampling variance.
Visman worked briefly in
Ottawaafter immigrating to Canada in 1951. Until his retirement in 1976, he headed the Western Regional Laboratories of the Department of Mines and Technical Surveys, which is nowadays known as Energy, Mines & Resources. These laboratories were located in Calgary until 1955 when they moved to Edmonton and are still operating alongside the Alberta Research Council at the Coal Research Centre in Devon, Alberta.
Visman wrote "Towards a Common Basis for the Sampling of Materials", Mines Branch Research Report R 93, which was published in July 1962. He participated in ASTM Committees D-5 on
Coaland Coke and E-11 on Statistics. ASTM D 2234 "Standard Practice for Collection of a Gross Sample of Coal" was the first internationally recognized standard to specify a precision estimate for a measured variable. Visman’s sampling experiment with small and large increments is described in ASTM D 2234, Annex A1. "Test Method for Determining the Variance Components of a Coal". Visman’s paper titled "A General Sampling Theory" was published in the November 1969 issue of Materials Research & Standards.
Dr Jan Visman was an accidental sampling expert because his true calling was coal processing but he became interested in sampling because of his need to understand this process. His innovative work inspired a great deal of progress in sampling theory and practice in many scientific disciplines. His brilliant mind succumbed long before he died on
February 19, 2006. Dr Jan Visman’s contribution to the bridging of the breach between sampling theory and sampling practice for materials in bulk should be remembered.
*Gy, P, "L’Ếchantillonnage des Minerais en Vrac, Tome 1 Théorie Générale", Jan 1967, "Revue de L’Industrie Minérale"
*Gy, P, "L’Ếchantillonnage des Minerais en Vrac, Tome 2, Théorie Générale Erreurs Opératoires Complements", Sep 1971, "Revue de L’Industrie Minérale"
*Merks, J W, "Sampling and Weighing of Bulk Solids", Trans Tech Publications, Claustall-Zellerfeld, 1985
*Visman, J, "De monsterneming van heterogene binomiale korrelmengsels, in het bijzonder steenkool", PhD Thesis, Delft, 1947
*Visman, J, "Towards a Common Basis for the Sampling of Materials", Research Report R93, Department of Mines, Ottawa, 1962
*Visman, J, "A General Sampling Theory", "Materials Research and Standards", Vol 9, No 11, 1969
* [http://www4.stat.ncsu.edu/~cproctor/A_Review.htm Visman's sampling equations]
* [http://www.em.gov.bc.ca/DL/COALReports/013.pdf Visman's sampling theory in practice]
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