ISO INTERNATIONAL STANDARD 6139 First edition 1993-08-01 Aluminium ores -- Experimental determination of the heterogeneity of distribution of a lot Mineraisalumineux- -Détermination experimentale de I'hétérogéneite dedistributiond'un lot Reference number ISO6139:1993(E) ISO 6139:1993(E) Foreword IsO (the International Organization for Standardization)is a worldwide federation of national standards bodies (Iso member bodies). The work of preparing International Standards is normally carried out through isO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented onthat committee.International organizations,governmental and non-governmental, in liaison with IsO, also take part in the work. Iso collaborates closely with the International Electrotechnical Commission (lEC)onallmattersofelectrotechnicalstandardization. Draft International Standards adopted by the technical committees are Standard requires approval by at least 75 % of the member bodies casting a vote. International Standard ISO 6139 was prepared by Technical Committee ISO/TC 129, Aluminium ores, Sub-Committee SC 1, Sampling. ISO 1993 by any means,electronic or mechanical, including photocopying and microfilm,without per- mission in writing from the publisher. International Organization for Standardization Case Postale 56 · CH-1211 Geneve 20· Switzerland Printed in Switzerland ii INTERNATIONAL STANDARD ISO6139:1993(E) Aluminium ores -- Experimental determination of the heterogeneity of distribution of a lot 1 Scope ance can be reduced only by increasing the number ofincrements. This International Standard specifies experimental methods for evaluating the heterogeneity of distri- 3.2 Method of estimating the heterogeneity bution of aluminium ores, for the purpose of deter- of distribution miningtheminimumnumberof primaryincrements and consequently the sampling scheme. The heterogeneity of distribution, characterized by the distributionvariance,isdeterminedbyexperimentally measuring the sampling variance. However, because 2 Normative references both the composition variance(V)and distribution variance (Vo) contribute to the measured sampling The following standards contain provisions which, variance, it is necessary to separate these two com- through reference in this text, constitute provisions ponents. This is achieved by measuring the sampling of this International Standard. At the time of publi- variance at two different increment masses. cation, the editions indicated were valid. All standards are subject to revision, and parties to agreements Two methods of data analysis are permitted. The first based on this International Standard are encouraged (see 5.1) is based on Visman's theory of sampling to investigate the possibility of applying the most re- which uses classical statistics. This method gives cent: editions of the standards indicated below. conservative estimates of the sampling variance and Members of IEC and ISO maintain registers of cur- hence the distribution variance. The second method rently valid International Standards. (see 5.2) is based on the variogram which takes into accountserial correlation between adjacent in Is08685:1992,Aluminium ores Sampling pro- crements and the spacing between increments. It cedures. gives a better estimate of the sampling variance and should be used to optimize the sampling scheme. Is010277:—-1,Aluminium ores Experimental methods for checking the precision of sampling. In both cases, the variance of sample preparation and analysis shall be determined separately in accordance with is0 10277, and subtracted from the measured 3 General variances. 3.1 Origin of heterogeneity of distribution 3.3 Characteristics measured The heterogeneity of distribution is a measure of the The quality characteristics chosen for measuring the distribution variability of the aluminium ore and hence heterogeneity of distribution should be those that ar