 Het belong van automatische monsterneming; mogelijkheden en toepas‐singen*J. Visman Statistica Neerlandica, 1950, vol. 4, issue 5, 184-194 Abstract: Automatic sampling; its possibilities and applications. The problem considered is that of sampling a lot of coal or ore in order to determine the average content of some essential component; as a particular example the sampling of coal for ash content is taken. Three sources of error are considered, namely: 1 the sampling error, depending on the size of, and the distribution of ash content amongst, the grains; this error can be reduced by taking a large sample; 2 the error due to inhomogeneities in the lot, which can be cut down by using a gross sample composed of a large number of increments; and 3 the error in the analysis, including the errors introduced by grinding and dividing the gross sample into the final sample of about 1 gram used for the determination of ash content. The accuracy (a) corresponding to 99% confidence limits is expressed in a simple formula, (1), in which the influence of each of the sources of error is represented by a separate term. Taking as a lot the coal produced at a mine during a shift, the formula shows that, to achieve a reasonable accuracy of a =i/0 ash, at least some 150 to 200 increments have to be taken, the second sourse of error (inhomogeneity of the lot) being by far the most important one. The size of the increments can be relatively small so that the weight of the gross sample stays within acceptable limits. This large number of increments necessitates the use of an automatic sampling procedure. In § 3 a sampler developed and installed at one of the Dutch State Mines is described together with the precautions required to prevent bias in the samples due tj segregation of the coal across the conveyor belt. For further details the English reader may be referred to Fuel 19, 101–105,1950. Date: 1950 Downloads: (external link) Related works: Export reference: BibTeX RIS (EndNote, ProCite, RefMan) HTML/Text Persistent link: https://EconPapers.repec.org/RePEc:bla:stanee:v:4:y:1950:i:5:p:184-194 Ordering information: This journal article can be ordered from Access Statistics for this article Statistica Neerlandica is currently edited by Miroslav Ristic, Marijtje van Duijn and Nan van Geloven More articles in Statistica Neerlandica from Netherlands Society for Statistics and Operations Research |
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