Jan Visman
Encyclopedia
Jan Visman played a key role in building a bridge between sampling
theory with its homogeneous populations and 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 Delft University of Technology
, 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 sample
s selected from heterogeneous sampling units of coal. In fact, he had gathered so much valuable information that he was encouraged to write a PhD
thesis 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 variance
of 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 variability
between 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. The distribution heterogeneity causes spatial dependence between measured values in ordered sets determined in sampling units and sample spaces.
Visman worked briefly in Ottawa
after 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 Coal
and 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 passed away 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.
Sampling (statistics)
In statistics and survey methodology, sampling is concerned with the selection of a subset of individuals from within a population to estimate characteristics of the whole population....
theory with its homogeneous populations and sampling practice with its heterogeneous sampling units and sample spaces. Born in Deventer
Deventer
Deventer is a municipality and city in the Salland region of the Dutch province of Overijssel. Deventer is largely situated on the east bank of the river IJssel, but also has a small part of its territory on the west bank. In 2005 the municipality of Bathmen Deventer is a municipality and city in...
, The Netherlands, on July 2, 1914, Visman studied mining engineering at the Delft University of Technology
Delft University of Technology
Delft University of Technology , also known as TU Delft, is the largest and oldest Dutch public technical university, located in Delft, Netherlands...
, 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 sample
Sampling (music)
In music, sampling is the act of taking a portion, or sample, of one sound recording and reusing it as an instrument or a different sound recording of a song or piece. Sampling was originally developed by experimental musicians working with musique concrète and electroacoustic music, who physically...
s selected from heterogeneous sampling units of coal. In fact, he had gathered so much valuable information that he was encouraged to write a PhD
PHD
PHD may refer to:*Ph.D., a doctorate of philosophy*Ph.D. , a 1980s British group*PHD finger, a protein sequence*PHD Mountain Software, an outdoor clothing and equipment company*PhD Docbook renderer, an XML renderer...
thesis 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 variance
Variance
In probability theory and statistics, the variance is a measure of how far a set of numbers is spread out. It is one of several descriptors of a probability distribution, describing how far the numbers lie from the mean . In particular, the variance is one of the moments of a distribution...
of 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 variability
Variability
The term variability, "the state or characteristic of being variable", describes how spread out or closely clustered a set of data is. This may be applied to many different subjects:*Climate variability...
between 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. The distribution heterogeneity causes spatial dependence between measured values in ordered sets determined in sampling units and sample spaces.
Visman worked briefly in Ottawa
Ottawa
Ottawa is the capital of Canada, the second largest city in the Province of Ontario, and the fourth largest city in the country. The city is located on the south bank of the Ottawa River in the eastern portion of Southern Ontario...
after 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
Devon, Alberta
Devon is a town in the province of Alberta, Canada, situated southwest of Edmonton, the provincial capital, and located along the banks of the North Saskatchewan River.- History :Devon owes its existence to one of the largest oil discoveries in the world...
.
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 Coal
Coal
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...
and Coke
Coke (fuel)
Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...
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 passed away 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.