1、BRITISH STANDARD BS ISO3086:2006Iron ores Experimental methodsfor checking the bias ofsamplingICS 73.060.10g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g4
2、7g36g58February 2010Incorporating corrigendumNational forewordThis British Standard is the UK implementation of ISO 3086:2006. It supersedes BS ISO 3086:1998 and BS 5662-3:1987 which are withdrawn.The UK participation in its preparation was entrusted to Technical Committee ISE/58, Iron ores.A list o
3、f organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal ob
4、ligations.BS ISO 3086:2006This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 May 2006 BSI 2010Amendments/corrigenda issued since publicationDate Comments 28 February 2010 Supersession text amendedISBN 978 0 580 69922 1Reference numberISO 3086
5、:2006(E)INTERNATIONAL STANDARD ISO3086Fourth edition2006-04-15Iron ores Experimental methods for checking the bias of sampling BS ISO 3086:2006ii iiiContents Page Foreword iv 1 Scope . 1 2 Normative references . 1 3 Terms and definitions. 1 4 Principle. 2 5 General conditions . 2 6 Sampling and samp
6、le preparation methods 2 6.1 Sampling 2 6.2 Sample preparation 2 7 Analysis of experimental data . 3 7.1 Computation of the differences. 3 7.2 Determination of the mean and the standard deviation of the differences 3 7.3 Test for outliers Grubbs test 3 7.4 Selection of data for use in statistical te
7、st for bias. 5 7.4.1 Consideration of outliers whose causes are assignable 5 7.4.2 Consideration of outliers whose causes are not assignable. 5 7.4.3 Consideration of amount of data remaining 5 7.5 Statistical test for bias 5 7.5.1 Determination of the confidence interval for d 5 7.5.2 Interpretatio
8、n of confidence interval 6 8 Test report . 7 Annex A (normative) Flowsheets of the statistical analysis 8 Annex B (informative) Numerical examples of experiments 11 BS ISO 3086:2006iv Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bo
9、dies (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 on that committee. International organizatio
10、ns, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the
11、ISO/IEC Directives, Part 2. The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of th
12、e member bodies casting a vote. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 3086 was prepared by Technical Committee ISO/TC 102, Iron ore and
13、 direct reduced iron, Subcommittee SC 1, Sampling. This fourth edition cancels and replaces the third edition (ISO 3086:1998), which has been technically revised. BS ISO 3086:20061Iron ores Experimental methods for checking the bias of sampling 1 Scope This International Standard specifies experimen
14、tal methods for checking the bias of sampling of iron ores, when sampling is carried out in accordance with the methods specified in ISO 3082, having as reference a stopped-belt sampling method. It is recommended that an inspection of the mechanical sampling system be carried out before conducting b
15、ias testing. Sampling systems not completely in accordance with ISO 3082 are not always expected to be biased. Therefore, bias checking may be done when there is some disagreement about the importance of some departure from the conditions of ISO 3082. If one party argues that the bias is likely to b
16、e substantial under some particular set of conditions then bias testing should mostly be done when those conditions apply. NOTE The method for analysis of experimental data described here may also be applied: a) for checking the bias of sample preparation of iron ores, having as reference the method
17、s for sampling preparation according to ISO 3082; b) for checking the bias of size distribution of iron ores by sieving, having as reference the hand sieving methods according to ISO 4701; c) for checking a possibly significant difference in the results obtained from the samples of one lot collected
18、 at different places, for example, a loading point and unloading point. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced
19、 document (including any amendments) applies. ISO 3082:2000, Iron ores Sampling and sample preparation procedures ISO 3085:2002, Iron ores Experimental methods for checking the precision of sampling, sample preparation and measurement ISO 11323:2002, Iron ore and direct reduced iron Vocabulary 3 Ter
20、ms and definitions For the purposes of this document, the terms and definitions given in ISO 11323 apply. BS ISO 3086:20062 4 Principle The results obtained from the method to be checked (referred to as method B) are compared with the results of a reference method (referred to as method A) which is
21、considered to produce practically unbiased results, from technical and empirical viewpoints. In the event of there being no significant difference, in a statistical sense, between the results obtained by method B and method A, method B may be adopted as a routine method. This difference is assessed
22、by comparing a 90 % confidence interval for the true average bias with the relevant bias, (see 5.2). 5 General conditions 5.1 The number of paired sets of measurement shall not be less than ten. The number of further tests required depends on the results of the outlier test and of the statistical an
23、alysis of the confidence interval for the true average bias, based on at least ten paired sets. NOTE A paired set of measurement is a paired measurement data of samples, which are sampled by methods A and B, and prepared and measured in the same way, for identical material. 5.2 The relevant bias, ,
24、which is considered large enough to justify the likely expense of reducing the average bias, shall be decided beforehand. As a guide, is likely to be less than SPM, the standard deviation for sampling, sample preparation and measurement, determined according to ISO 3085. NOTE If the experiment is ai
25、med at checking sample preparation only, the value of is likely to be less than PM, determined according to ISO 3085. 5.3 Quality characteristics, such as total iron content, moisture content, size distribution and physical properties, may be used. 6 Sampling and sample preparation methods 6.1 Sampl
26、ing The reference method, method A, for checking the bias of sampling is a stopped-belt sampling method in accordance with ISO 3082. Method A: take each increment from the full width and thickness of the ore stream on the stopped conveyor at a specified place, for a length of belt more than three ti
27、mes the nominal top size or 30 mm, whichever is the greater. The method to be checked, method B, carried out according to ISO 3082 as far as possible, shall be compared with method A for the same material. Method B: sampling methods, such as sampling from moving conveyors with a mechanical sampler a
28、nd sampling during the transfer to or from ships and wagons, are examples of method B. Samples from Methods A and B shall be taken as close together as possible. This is particularly important for ore streams which are known to be variable. 6.2 Sample preparation 6.2.1 Increments obtained from one l
29、ot, in accordance with methods A and B, are made up into two gross samples, A and B. BS ISO 3086:200636.2.2 The gross samples, A and B, are subjected, in the same manner, to sample preparation as specified in ISO 3082, and tested as specified in the relevant International Standards separately, and a
30、 pair of measurements obtained. 6.2.3 The above procedure is performed on ten or more lots (see 5.1). When increments for methods A and B can be taken from closely adjacent portions of the ore, it is recommended that sample preparation and testing be carried out on individual increments or on combin
31、ations of a small number of adjacent increments. This allows comparisons of ten or more pairs of measurements to be made more quickly than if measurements were only made on entire lots. The above comparison of measurements should be made on pairs of increments taken from several lots, preferably of
32、the same type of ore. However, it is not permitted to combine a number of paired results, originating from both increments and gross samples. It should be either a number of pairs from increments or from gross samples. NOTE Given the cost and inconvenience of stopped-belt sampling, it is generally e
33、conomic to conduct sample preparation and measurement in duplicate and with great care so that the number of stopped-belt samples might be reduced. 7 Analysis of experimental data NOTE The procedures described in 7.1 to 7.5 are also shown in the form of a flowsheet in Annex A (normative). 7.1 Comput
34、ation of the differences 7.1.1 Denote measurements obtained in accordance with methods A and B, by xAiand xBi, respectively. When sampling preparation and measurement have been conducted in duplicate, these measurements will be averaged. 7.1.2 Calculate the difference, di, between xAiand xBiusing th
35、e equation: BA1, 2, .iiidx x i k= = (1) where k is the number of paired sets of measurements. 7.2 Determination of the mean and the standard deviation of the differences 7.2.1 Calculate the mean of the differences, ,d with one decimal place more than that used in the measurements themselves: 1iddk=(
36、2) 7.2.2 Calculate the sum of squares, SSd, and the standard deviation of the differences, Sd, with one decimal place more than that used in the measurements themselves: ()221SSdi iddk=(3) SS(1)ddSk=(4) 7.3 Test for outliers Grubbs test 7.3.1 Sort diinto ascending order. BS ISO 3086:20064 7.3.2 Calc
37、ulate the Grubbs test statistics Gkand G1, using the following equations: kkdddGS= (5) 11dddGS= (6) where dkis the largest value of di; d1is the smallest value of di; 7.3.3 Choose the larger of Gkand G1. 7.3.4 Compare the larger of Gkand G1with the critical value for Grubbs test at the 5 % significa
38、nce level according to Table 1. Table 1 Critical values for Grubbs outlier test k Critical value (5 %) k Critical value(5 %) k Critical value (5 %) 6 1,887 12 2,412 18 2,651 7 2,020 13 2,462 19 2,681 8 2,126 14 2,507 20 2,709 9 2,215 15 2,549 21 2,733 10 2,290 16 2,585 22 2,758 11 2,355 17 2,620 23
39、2,781 NOTE Critical values for Grubbs test for a wider range of numbers of observations, and for additional significance levels, are given in Grubbs, F. E. and Beck, G. (1972) Extension of sample sizes and percentage points for significance tests of outlying observations, Technometrics 14, pp. 847-8
40、54. 7.3.4.1 If the larger of Gkand G1is less than or equal to the critical value, conclude that there is no outlier. Proceed with 7.5. 7.3.4.2 If the larger of Gkand G1is larger than the critical value: 7.3.4.2.1 If the larger is Gk, conclude that the largest value of the difference, dk, is an outli
41、er. 7.3.4.2.2 If the larger is G1, conclude that the smallest value of the difference, d1, is an outlier. 7.3.5 Exclude the outlier di, repeat the procedure described in 7.2 to 7.3.3. 7.3.6 Compare the larger of Gkand G1with the critical value for Grubbs test at 5 % significance level according to T
42、able 1. 7.3.6.1 If the larger of Gkand G1is less than or equal to the critical value, conclude that there is no outlier and proceed with 7.4. BS ISO 3086:200657.3.6.2 If the larger of Gkand G1is larger than the critical value: 7.3.6.2.1 If the larger is Gk, conclude that the largest value of the dif
43、ference, dk, is an outlier. 7.3.6.2.2 If the larger is G1, conclude that the smallest value of the difference, d1, is an outlier. 7.3.7 If at least 60 % of the initial set of data remain, proceed with 7.3.5. 7.3.8 If not, stop the outlier test, reinstate all outliers and proceed with 7.5. 7.4 Select
44、ion of data for use in statistical test for bias 7.4.1 Consideration of outliers whose causes are assignable Once outliers have been detected by Grubbs test, consideration should be given to assignable causes for those outliers, such as change in the level of moisture, partial blockage of a cutter o
45、pening, or changes in characteristics of the material being sampled. For each outlier whose cause can be determined with reasonable confidence: If the cause is likely to occur in the future then reinstate the outlier, but if the cause is not likely to occur in the future then exclude the outlier. 7.
46、4.2 Consideration of outliers whose causes are not assignable If the cause of an outlier could not be determined with reasonable confidence then the outlier should be excluded. 7.4.3 Consideration of amount of data remaining If at least 10 paired sets of measurements remain, proceed with 7.5. If not
47、, carry out more sampling and testing to complete at least 10 paired sets of measurements, reinstate the outliers excluded, except those which have an assignable cause and are not likely to occur in the future, and repeat 7.1 to 7.4 since differences previously classified as outliers may or may not
48、be found to be outliers when Grubbs test is applied to the larger set of data. 7.5 Statistical test for bias 7.5.1 Determination of the confidence interval for d 7.5.1.1 Calculate the mean and standard deviation of the differences which have not been rejected as outliers. 7.5.1.2 Calculate the lower
49、 limit of the confidence interval LL and the upper limit of the confidence interval UL with the same number of decimal places of that used in the measurements themselves, using the equations: LLdSdtk= (7) ULdSdtk=+ (8) where t is the value of Students t distribution for (k 1) degrees of freedom and is given in Table 2; k is the number of paired sets of measurements which have not been rejected as outliers. BS ISO 3086:20066 Table 2 is prepared in such a way that when entering with a number of paired sets of measurement, k, the corresponding t v
