SIST EN ISO 4259-1:2018
(Main)Petroleum and related products - Precision of measurement methods and results - Part 1: Determination of precision data in relation to methods of test (ISO 4259-1:2017)
Petroleum and related products - Precision of measurement methods and results - Part 1: Determination of precision data in relation to methods of test (ISO 4259-1:2017)
This document specifies the methodology for the design of an Interlaboratory Study (ILS) and
calculation of precision estimates of a test method specified by the study. In particular, it defines the
relevant statistical terms (Clause 3), the procedures to be adopted in the planning of ILS to determine
the precision of a test method (Clause 4), and the method of calculating the precision from the results of
such a study (Clauses 5 and 6).
The procedures in this document have been designed specifically for petroleum and petroleum related
products, which are normally considered as homogeneous. However, the procedures described in this
document can also be applied to other types of homogeneous products. Careful investigations are
necessary before applying this document to products for which the assumption of homogeneity can be
questioned.
Mineralölerzeugnisse - Präzision von Messverfahren und Ergebnissen - Teil 1: Bestimmung der Werte für die Präzision von Prüfverfahren (ISO 4259-1:2017)
Diese Internationale Norm umfasst die Methodik für die Auslegung einer Laborvergleichsuntersuchung (ILS, en: Interlaboratory Study) und die Berechnung von Schätzwerten für die Präzision eines durch die Untersuchung festgelegten Prüfverfahrens. Insbesondere enthält sie Definitionen für wichtige statistische Begriffe (siehe Abschnitt 3), die zu ergreifenden Maßnahmen für die Planung von ILS zur Bestimmung der Präzision eines Prüfverfahrens (siehe Abschnitt 4) und die Methodik zur Berechnung der Präzision aus den Ergebnissen einer derartigen Untersuchung (Abschnitte 5 und 6).
Die Verfahren in dieser Internationalen Norm wurden speziell für Mineralölerzeugnisse und verwandte Produkte entwickelt, die im Allgemeinen homogene Produkte sind. Die in dieser Internationalen Norm beschriebenen Verfahren können jedoch auch auf andere Arten von homogenen Erzeugnissen angewendet werden. Vor der Anwendung dieser Internationalen Norm auf andere Erzeugnisse, bei denen die Ausnahme der Homogenität hinterfragt werden kann, sind sorgfältige Untersuchungen hinsichtlich der Anwendbarkeit erforderlich.
Produits pétroliers - Fidélité des méthodes de mesure et des résultats - Partie 1: Détermination des valeurs de fidélité relatives aux méthodes d'essai (ISO 4259-1:2017)
ISO 4259-1:2017 spécifié la méthodologie pour la conception d'un essai interlaboratoires (ILS) et pour le calcul des estimations de fidélité d'une méthode d'essai spécifié par cet ILS. En particulier, il définit les termes statistiques concernés (Article 3), les procédures à suivre dans l'organisation d'un ILS destiné à déterminer la fidélité d'une méthode d'essai (Article 4) et la méthode de calcul de la fidélité à partir des résultats d'un tel ILS (Articles 5 et 6).
Les procédures de l' ISO 4259-1:2017 ont été conçues spécifiquement pour les produits pétroliers et leurs produits connexes qui sont normalement considérés homogènes. Les procédures décrites dans le présent document peuvent cependant aussi s'appliquer à d'autres types de produits homogènes. Il est nécessaire de procéder à des contrôles attentifs avant d'appliquer ce document à des produits pour lesquels la présomption d'homogénéité peut être mise en question.
Nafta in sorodni proizvodi - Natančnost merilnih metod in rezultatov - 1. del: Določevanje natančnosti preskusnih metod (ISO 4259-1:2017)
Ta dokument opredeljuje metodologijo za načrtovanje medlaboratorijske študije (ILS) in izračun stopnje natančnosti preskusne metode, ki jo je določila študija. Še zlasti določa ustrezne statistične izraze (točka 3), postopke za načrtovanje medlaboratorijske študije za določitev natančnosti preskusne metode (točka 4) in metodo za izračun natančnosti na podlagi rezultatov take študije (točki 5 in 6).
Postopki v tem dokumentu so bili zasnovani posebej za nafto in sorodne
proizvode, ki se običajno obravnavajo kot homogeni. Kljub temu pa se postopke, opisane v tem
dokumentu, lahko uporablja tudi za druge vrste homogenih proizvodov. Pred uporabo tega dokumenta za proizvode, pri katerih je predpostavka o homogenosti lahko vprašljiva, so potrebne
temeljite preiskave.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 4259-1:2018
01-februar-2018
1DGRPHãþD
SIST EN ISO 4259:2006
1DIWDLQVRURGQLSURL]YRGL1DWDQþQRVWPHULOQLKPHWRGLQUH]XOWDWRYGHO
'RORþHYDQMHQDWDQþQRVWLSUHVNXVQLKPHWRG ,62
Petroleum and related products - Precision of measurement methods and results - Part
1: Determination of precision data in relation to methods of test (ISO 4259-1:2017)
Mineralölerzeugnisse - Präzision von Messverfahren und Ergebnissen - Teil 1:
Bestimmung der Werte für die Präzision von Prüfverfahren (ISO 4259-1:2017)
Produits pétroliers - Fidélité des méthodes de mesure et des résultats - Partie 1:
Détermination des valeurs de fidélité relatives aux méthodes d'essai (ISO 4259-1:2017)
Ta slovenski standard je istoveten z: EN ISO 4259-1:2017
ICS:
75.080 Naftni proizvodi na splošno Petroleum products in
general
75.180.30 Oprema za merjenje Volumetric equipment and
prostornine in merjenje measurements
SIST EN ISO 4259-1:2018 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 4259-1:2018
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SIST EN ISO 4259-1:2018
EN ISO 4259-1
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2017
EUROPÄISCHE NORM
ICS 75.080 Supersedes EN ISO 4259:2006
English Version
Petroleum and related products - Precision of
measurement methods and results - Part 1: Determination
of precision data in relation to methods of test (ISO 4259-
1:2017)
Produits pétroliers et connexes - Fidélité des méthodes Mineralölerzeugnisse - Präzision von Messverfahren
de mesure et de leurs résultats - Partie 1: und Ergebnissen - Teil 1: Bestimmung der Werte für
Détermination des valeurs de fidélité relatives aux die Präzision von Prüfverfahren (ISO 4259-1:2017)
méthodes d'essai (ISO 4259-1:2017)
This European Standard was approved by CEN on 27 October 2017.
CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2017 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 4259-1:2017 E
worldwide for CEN national Members.
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SIST EN ISO 4259-1:2018
EN ISO 4259-1:2017 (E)
Contents Page
European foreword . 3
2
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SIST EN ISO 4259-1:2018
EN ISO 4259-1:2017 (E)
European foreword
This document (EN ISO 4259-1:2017) has been prepared by Technical Committee ISO/TC 28
"Petroleum and related products, fuels and lubricants from natural or synthetic sources" in
collaboration with Technical Committee CEN/TC 19 “Gaseous and liquid fuels, lubricants and related
products of petroleum, synthetic and biological origin” the secretariat of which is held by NEN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by June 2018, and conflicting national standards shall be
withdrawn at the latest by June 2018.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN ISO 4259:2006.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 4259-1:2017 has been approved by CEN as EN ISO 4259-1:2017 without any
modification.
3
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SIST EN ISO 4259-1:2018
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SIST EN ISO 4259-1:2018
INTERNATIONAL ISO
STANDARD 4259-1
First edition
2017-11
Petroleum and related products —
Precision of measurement methods
and results —
Part 1:
Determination of precision data in
relation to methods of test
Produits pétroliers — Fidélité des méthodes de mesure et des
résultats —
Partie 1: Détermination des valeurs de fidélité relatives aux
méthodes d'essai
Reference number
ISO 4259-1:2017(E)
©
ISO 2017
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SIST EN ISO 4259-1:2018
ISO 4259-1:2017(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2017, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2017 – All rights reserved
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SIST EN ISO 4259-1:2018
ISO 4259-1:2017(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Stages in the planning of an interlaboratory study for the determination of the
precision of a test method . 4
4.1 General . 4
4.2 Preparing a draft method of test . 5
4.3 Planning a pilot study with at least two laboratories . 5
4.4 Planning the ILS . 5
4.5 Executing the ILS . 6
5 Statistical treatment of ILS results . 7
5.1 General recommendation . 7
5.2 Pre-screen using GESD technique . 7
5.3 Transformation of data and outlier tests . 8
5.3.1 General. 8
5.3.2 Outlier identification after pre-screening .11
5.3.3 Uniformity of repeatability .11
5.3.4 Uniformity of reproducibility.11
5.4 Rejection of complete data (from all laboratories) for a sample .11
5.5 Estimating missing or rejected values .12
5.5.1 One of the two repeat values missing or rejected .12
5.5.2 Both repeat values missing or rejected .12
5.6 Rejection test for outlying laboratories .12
5.7 Confirmation of selected transformation .13
5.7.1 General.13
5.7.2 Identification of excessively influential sample(s) .13
6 Analysis of variance, calculation and expression of precision estimates .14
6.1 General .14
6.2 Analysis of variance .14
6.2.1 Forming the sums of squares for the laboratories × samples interaction
sum of squares .14
6.2.2 Forming the sum of squares for the exact analysis of variance .15
6.2.3 Degrees of freedom . .15
6.2.4 Mean squares and analysis of variance .15
6.3 Expectation of mean squares and calculation of precision estimates .15
6.3.1 Expectation of mean squares with no estimated values .15
6.3.2 Expectation of mean squares with estimated values .16
6.3.3 Calculation of precision estimates .17
6.4 Expression of precision estimates of a method of test .18
6.5 Specification of scope for the test method .19
7 R/r ratio .20
Annex A (normative) Determination of number of samples required.21
Annex B (informative) Derivation of formula for estimating the number of laboratories and
samples required to meet minimum 30 degrees of freedom .23
Annex C (normative) Notation and tests .25
Annex D (normative) Illustration of procedures using ILS results for Bromine Number and
statistical tables .30
© ISO 2017 – All rights reserved iii
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SIST EN ISO 4259-1:2018
ISO 4259-1:2017(E)
Annex E (normative) Types of dependence and corresponding transformations.49
Annex F (normative) Weighted linear regression analysis .55
Annex G (normative) Rules for rounding .62
Annex H (normative) GESD technique to simultaneously identify multiple outliers in a data set .64
Annex I (informative) Glossary.72
Bibliography .75
iv © ISO 2017 – All rights reserved
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SIST EN ISO 4259-1:2018
ISO 4259-1:2017(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 on that 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 (IEC) on all matters of
electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the
World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following
URL: www.iso.org/iso/foreword.html.
This document was prepared by Technical Committee ISO/TC 28, Petroleum and related products, fuels
and lubricants from natural or synthetic sources.
This first edition of ISO 4259-1, together with ISO 4259-2, cancels and replaces ISO 4259, which has
been technically revised.
A list of all parts in the ISO 4259 series can be found on the ISO website.
© ISO 2017 – All rights reserved v
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SIST EN ISO 4259-1:2018
ISO 4259-1:2017(E)
Introduction
For purposes of quality control and to check compliance with specifications, the properties of
commercial petroleum products are assessed by standard laboratory test methods. Two or more
measurements of the same property of a specific sample by a specific test method, or, by different test
methods that purport to measure the same property, will not usually give exactly the same result. It is,
therefore, necessary to take proper account of this fact, by arriving at statistically based estimates of
the precision for a method, i.e. an objective measure of the degree of agreement expected between two
or more results obtained in specified circumstances.
[1]
This document makes reference to ISO 3534-2 , which gives a different definition of true value
(see 3.23). This document also refers to ISO 5725-2. The latter is required in particular and unusual
circumstances (see 5.3.1) for the purpose of estimating precision.
The two parts of ISO 4259 encompass both the derivation of precision estimates and the application
[2]
of precision data. They combine the information in ASTM D6300 regarding the determination of the
[3]
precision estimates and the information in ASTM D3244 for the utilization of test data.
A glossary of the variables used in this document and ISO 4259-2 is included as Annex I in this document.
vi © ISO 2017 – All rights reserved
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SIST EN ISO 4259-1:2018
INTERNATIONAL STANDARD ISO 4259-1:2017(E)
Petroleum and related products — Precision of
measurement methods and results —
Part 1:
Determination of precision data in relation to methods of
test
1 Scope
This document specifies the methodology for the design of an Interlaboratory Study (ILS) and
calculation of precision estimates of a test method specified by the study. In particular, it defines the
relevant statistical terms (Clause 3), the procedures to be adopted in the planning of ILS to determine
the precision of a test method (Clause 4), and the method of calculating the precision from the results of
such a study (Clauses 5 and 6).
The procedures in this document have been designed specifically for petroleum and petroleum related
products, which are normally considered as homogeneous. However, the procedures described in this
document can also be applied to other types of homogeneous products. Careful investigations are
necessary before applying this document to products for which the assumption of homogeneity can be
questioned.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 5725-2, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic method
for the determination of repeatability and reproducibility of a standard measurement method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at http://www.electropedia.org/
3.1
analysis of variance
ANOVA
technique that enables the total variance of a method to be broken down into its component factors
3.2
accepted reference value
ARV
agreed-upon reference value for a specific property of a material determined using an accepted
reference method and protocol, e.g. derived from an ILS
© ISO 2017 – All rights reserved 1
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SIST EN ISO 4259-1:2018
ISO 4259-1:2017(E)
3.3
between laboratory variance
component of the total variance attributable to the difference between the means of different
laboratories
Note 1 to entry: When results obtained by more than one laboratory are compared, the scatter is usually wider
than when the same number of tests is carried out by a single laboratory, and there is some variation between
means obtained by different laboratories. These give rise to the between laboratory variance which is that
component of the overall variance due to the difference in the means obtained by different laboratories.
Note 2 to entry: There is a corresponding definition for between operator variance.
Note 3 to entry: The term “between laboratory” is often shortened to “laboratory” when used to qualify
representative parameters of the dispersion of the population of results, for example as “laboratory variance”.
3.4
bias
difference between the population mean of test results from a very large number
of different laboratories for the property of a material obtained using a specific test method versus the
accepted reference value for the property where this is available
Note 1 to entry: See Note 1 to entry in 3.13 for an interpretation of “population mean of test results”.
3.5
blind coding
assignment of a different number to each sample so that no other identification or information on any
sample is given to the operator
3.6
check sample
sample taken at the place where a product is exchanged, i.e. where the responsibility for the product
quality passes from the supplier to the recipient
3.7
degrees of freedom
divisor used in the calculation of variance
Note 1 to entry: The definition applies strictly only in the simplest cases. Definitions for more complex cases are
beyond the scope of this document.
3.8
determination
process of carrying out the series of operations specified in a test method, whereby a single value is
obtained
3.9
interlaboratory study
ILS
study specifically designed to estimate the repeatability and reproducibility of a standard test method
achieved at a fixed point in time by multiple laboratories through the statistical analysis of their test
results obtained on aliquots prepared from multiple materials
3.10
known value
quantitative value for a property that can be theoretically derived or calculated by the preparation of
the sample
Note 1 to entry: The known value does not always exist, for example for empirical tests such as flash point.
3.11
mean
sum of a set of results divided by the number of results
2 © ISO 2017 – All rights reserved
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SIST EN ISO 4259-1:2018
ISO 4259-1:2017(E)
3.12
mean square
sum of squares divided by the degrees of freedom
3.13
normal distribution
probability distribution of a continuous random variable, x, such that, if x is any real number, the
probability density is as shown in Formula (1):
2
1 1 x−μ
fx =−exp, −∞<
()
2 σ
σ 2π
Note 1 to entry: In the context of modelling a distribution of test results, μ is the population mean, or true value
(see 3.23) of the property as determined by a specific test method; σ is the standard deviation of the normal
distribution used to describe the distribution of an infinite number of test results obtained using the same test
method by an infinite number of laboratories (σ > 0).
3.14
operator
person who normally and regularly carries out a particular test
3.15
outlier
result far enough in magnitude from other results to be considered not a part of the set
3.16
precision
closeness of agreement between the results obtained by applying the same test procedure several times
on essentially the same materials and under prescribed conditions
Note 1 to entry: The smaller the random part of the experimental error, the more precise the procedure.
3.17
random error
component of measurement error that in replicate measurements varies in an unpredictable manner
3.18
repeatability
limiting value for the difference between two independent results obtained in the normal and correct
operation of the same method, for test material considered to be the same, within a short interval of
time, under the same test conditions, that is expected to be exceeded with a probability of 5% due to
random variation
Note 1 to entry: Same test conditions are to be considered as same operator, same apparatus, same calibration
and same laboratory.
Note 2 to entry: The representative parameter for the dispersion of the population that can be associated with
these results is repeatability standard deviation or repeatability variance. Repeatability refers to the maximum
difference attributable to random variation between two results obtained under the state of minimum random
variability. Therefore, the period of time during which repeat results are to be obtained should be short enough
to exclude time dependent variation, for example, variation caused by environmental changes, or variation
associated with multiple calibrations”.
Note 3 to entry: The term “repeatability” is not to be confused with the terms “between repeats” or “repeats”.
© ISO 2017 – All rights reserved 3
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SIST EN ISO 4259-1:2018
ISO 4259-1:2017(E)
3.19
reproducibility
limiting value for the difference between two independent results obtained in the normal and correct
operation of the same method, for test material considered to be the same, under different test
conditions, that is expected to be exceeded with a probability of 5 % due to random variation
Note 1 to entry: Different test conditions are to be considered as different operator, different apparatus, different
calibration, and different laboratory.
Note 2 to entry: The representative parameter of the dispersion of the population that can be associated with
these results is reproducibility standard deviation or reproducibility variance. Reproducibility refers to the
maximum difference attributable to random variation between two results obtained under the state of maximum
random variability.
3.20
result
final value obtained by following the complete set of instructions in a test method
Note 1 to entry: It is assumed that the result is rounded off according to the procedure specified in Annex G.
3.21
standard deviation
measure of the dispersion of a series of results around their mean, equal to the positive square root of
the variance and estimated by the positive square root of the mean square
3.22
sum of squares
sum of squares of the differences between a series of results and their mean
3.23
true value
for practical purposes, the value towards which the average of single results obtained by n laboratories
tends, as n tends towards infinity
Note 1 to entry: Such a true value is associated with the particular method of test.
[1]
Note 2 to entry: A different and idealized definition is given in ISO 3534-2 .
3.24
variance
mean of the squares of the deviation of a random variable from its mean, estimated by the mean square
4 Stages in the planning of an interlaboratory study for the determination of the
precision of a test method
4.1 General
The stages in planning an interlaboratory study (ILS) are as follows:
a) preparing a draft method of test;
b) planning a pilot study with at least two laboratories;
c) planning the ILS;
d) executing the ILS.
The four stages are described
...
SLOVENSKI STANDARD
oSIST prEN ISO 4259-1:2016
01-marec-2016
1DIWQLSURL]YRGL1DWDQþQRVWPHULOQLKPHWRGLQUH]XOWDWRYGHO 'RORþHYDQMH
VWRSHQMQDWDQþQRVWLSULSUHVNXVQLKPHWRGDK ,62',6
Petroleum products - Precision of measurement methods and results - Part 1:
Determination of precision data in relation to methods of test (ISO/DIS 4259-1:2016)
Mineralölerzeugnisse - Präzision von Messverfahren und Ergebnissen - Teil 1:
Bestimmung der Werte für die Präzision von Prüfverfahren (ISO/DIS 4259-1:2016)
Produits pétroliers - Fidélité des méthodes de mesure et des résultats - Partie 1:
Détermination des valeurs de fidélité relatives aux méthodes d'essai (ISO/DIS 4259-
1:2016)
Ta slovenski standard je istoveten z: prEN ISO 4259-1
ICS:
75.080 Naftni proizvodi na splošno Petroleum products in
general
75.180.30 Oprema za merjenje Volumetric equipment and
prostornine in merjenje measurements
oSIST prEN ISO 4259-1:2016 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
---------------------- Page: 1 ----------------------
oSIST prEN ISO 4259-1:2016
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oSIST prEN ISO 4259-1:2016
DRAFT INTERNATIONAL STANDARD
ISO/DIS 4259-1
ISO/TC 28 Secretariat: NEN
Voting begins on: Voting terminates on:
2016-01-14 2016-04-14
Petroleum products - Precision of measurement methods
and results —
Part 1:
Determination of precision data in relation to methods of
test
Produits pétroliers — Fidélité des méthodes de mesure et des résultats —
Partie 1: Détermination des valeurs de fidélité relatives aux méthodes d’essai
ICS: 75.080
ISO/CEN PARALLEL PROCESSING
This draft has been developed within the International Organization for
Standardization (ISO), and processed under the ISO lead mode of collaboration
as defined in the Vienna Agreement.
This draft is hereby submitted to the ISO member bodies and to the CEN member
bodies for a parallel five month enquiry.
Should this draft be accepted, a final draft, established on the basis of comments
received, will be submitted to a parallel two-month approval vote in ISO and
THIS DOCUMENT IS A DRAFT CIRCULATED
formal vote in CEN.
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
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Contents Page
Foreword . v
Introduction . vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Stages in the planning of an Interlaboratory Study for the determination of the precision
of a test method . 4
4.1 General . 4
4.2 Preparing a draft method of test . 4
4.3 Planning a pilot study with at least two laboratories . 5
4.4 Planning the ILS . 5
4.5 Executing the ILS . 6
5 Statistical treatment of ILS results . 7
5.1 General recommendation . 7
5.2 Pre-screen using GESD technique . 7
5.3 Transformation of data . 8
5.3.1 General . 8
5.3.2 Worked example . 9
5.4 Tests for outliers . 11
5.4.1 General . 11
5.4.2 Uniformity of repeatability . 11
5.4.3 Uniformity of reproducibility . 12
5.5 Rejection of complete data from a sample . 13
5.5.1 General . 13
5.5.2 Worked example . 13
5.6 Estimating missing or rejected values . 14
5.6.1 One of the two repeat values missing or rejected . 14
5.6.2 Both repeat values missing or rejected . 14
5.7 Rejection test for outlying laboratories . 15
5.7.1 General . 15
5.7.2 Worked example . 16
5.8 Confirmation of selected transformation . 16
5.8.1 General . 16
5.8.2 Identification of excessively influential sample(s) . 16
6 Analysis of variance, calculation and expression of precision estimates . 17
6.1 General . 17
6.2 Analysis of variance . 17
6.2.1 Forming the sums of squares for the laboratories samples interaction sum of squares . 17
6.2.2 Forming the sum of squares for the exact analysis of variance . 19
6.2.3 Degrees of freedom . 19
6.2.4 Mean squares and analysis of variance . 20
6.3 Expectation of mean squares and calculation of precision estimates . 20
6.3.1 Expectation of mean squares with no estimated values . 20
6.3.2 Expectation of mean squares with estimated values . 21
6.3.3 Calculation of precision estimates . 22
6.4 Expression of precision estimates of a method of test . 23
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7 R / r ratio . 24
Annex A (normative) Determination of number of samples required . 25
Annex B (informative) Derivation of formula for calculating the number of samples required . 27
B.1 Degrees of freedom . 27
B.2 Minimum degrees of freedom . 28
Annex C (normative) Notation and tests. 29
C.1 Introduction . 29
C.2 Array of duplicate results . 29
C.3 Array of sums of duplicate results. 29
C.4 Sums of squares and variances . 30
C.5 Cochran's test . 31
C.6 Hawkins' test . 31
C.7 Variance ratio test (F-test) . 33
Annex D (informative) Example results of test for determination of bromine number . 34
D.1 Statistical tables based on bromine number example . 34
D.2 Critical values of F . 39
D.3 Critical values of the normal distribution . 42
Annex E (normative) Types of dependence and corresponding transformations . 43
E.1 Types of dependence . 43
E.2 Transformation procedure . 44
Annex F (normative) Weighted linear regression analysis . 47
F.1 Explanation for the use of a dummy variable . 47
F.2 Derivation of weights used in regression analysis . 48
F.3 Computational procedure in regression analysis . 48
F.4 Worked example . 51
Annex G (normative) Rules for rounding off resultss . 55
Annex H (normative) GESD technique to simultaneously identify multiple outliers in a data set . 56
H.1 Background . 56
H.2 Application of GESD procedure to identify outliers in ILS data . 56
Bibliography . 55
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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 on that 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 (IEC) on all matters of electrotechnical standardization.
The procedures used to develop this document and those intended for its further maintenance are described
in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of
ISO documents should be noted. This document was drafted in accordance with the editorial rules of the
ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of any patent
rights identified during the development of the document will be in the Introduction and/or on the ISO list of
patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment,
as well as information about ISO's adherence to the WTO principles in the Technical Barriers to Trade (TBT)
see the following URL: Foreword - Supplementary information
The committee responsible for this document is ISO/TC 28, Petroleum products and related products of
synthetic or biological origin.
This edition, together with Part 2, cancels and replaces the third edition (ISO 4259:2006). It basically lays
down the content of the former Clauses 1 to 6 and connected, Annexes A to G, which have been thoroughly
reviewed and revised. The remaining Clauses and Annexes H and I of the third edition (ISO 4259:2006) are
cancelled and replaced by ISO 4259-2.
ISO 4259 consists of the following parts, under the general title Petroleum and related products — Precision
of measurement methods and results:
— Part 1:Determination of precision data in relation to methods of test;
— Part 2: Interpretation and Application of precision data in relation to methods of test.
A third part on monitoring and management of precision data in relation to methods of test is envisaged to be
published at a later point in time.
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Introduction
For purposes of quality control and to check compliance with specifications, the properties of commercial
petroleum products are assessed by standard laboratory test methods. Two or more measurements of the
same property of a specific sample by a specific test method, or, by different test methods that purport to
measure the same property, will not usually give exactly the same result. It is, therefore, necessary to take
proper account of this fact, by arriving at statistically-based estimates of the precision for a method, i.e. an
objective measure of the degree of agreement expected between two or more results obtained in specified
circumstances.
[1]
ISO 4259-1 makes reference to ISO 3534-2 , which gives a different definition of true value (see 3.26).
ISO 4259-1 also refers to ISO 5725-2. The latter is required in particular and unusual circumstances (see 5.2)
for the purpose of estimating precision.
The two parts of ISO 4259 encompass both the determination of precision estimates and the application of
[2]
precision data. It combines the information in ASTM D6300 regarding the determination of the precision
[3]
estimates and the information in ASTM D3244 for the utilization of test data. .
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Petroleum products — Precision of measurement methods and
results — Part 1: Determination and application of precision
data in relation to methods of test
1 Scope
This International Standard covers the methodology for the design of an Interlaboratory Study (ILS) and
calculation of precision estimates of a test method specified by the study. In particular, it contains definitions of
relevant statistical terms (Clause 3), the procedures to be adopted in the planning of ILS to determine the
precision of a test method (Clause 4), and the method of calculating the precision from the results of such a
study (Clauses 5 and 6).
The procedures in this International Standard have been designed specifically for petroleum and petroleum-
related products, which are normally homogeneous. However, the procedures described in this International
Standard can also be applied to other types of homogeneous products. Careful investigations are necessary
before applying this International Standard to products for which the assumption of homogeneity can be
questioned.
2 Normative references
The following referenced document is indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 5725-2:1994, Accuracy (trueness and precision) of measurement methods and results — Part 2: Basic
method for the determination of repeatability and reproducibility of a standard measurement method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
analysis of variance
technique that enables the total variance of a method to be broken down into its component factors
3.2
accepted reference value (ARV)
agreed upon reference value for a specific property of a material determined using an accepted reference
method and protocol.
3.3
between-laboratory variance
element of the total variance attributable to the difference between the mean values of different laboratories
Note 1 to entry: When results obtained by more than one laboratory are compared, the scatter is usually wider than when
the same number of tests is carried out by a single laboratory, and there is some variation between means obtained by
different laboratories. These give rise to the between-laboratory variance which is that component of the overall variance
due to the difference in the mean values obtained by different laboratories.
Note 2 to entry: There is a corresponding definition for between-operator variance.
1
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Note 3 to entry: The term “between-laboratory” is often shortened to “laboratory” when used to qualify representative
parameters of the dispersion of the population of results, for example as “laboratory variance”.
3.4
bias (of a test method)
difference between the population mean of test results from a very large number of different laboratories for
the property of a material obtained using a specific test method versus the accepted reference value for the
property where this is available
Note 1 to entry: See note entry in 3.13 for an interpretation of "population mean of test results".
3.5
blind coding
assignment of a different number to each sample so that no other identification or information on any sample
is given to the operator
3.6
check sample
sample taken at the place where a product is exchanged, i.e. where the responsibility for the product quality
passes from the supplier to the recipient
3.7
degrees of freedom
divisor used in the calculation of variance
Note 1 to entry: The definition applies strictly only in the simplest cases. Definitions for more complex cases are beyond
the scope of this International Standard.
3.8
determination
process of carrying out the series of operations specified in a test method, whereby a single value is obtained
3.9
interlaboratory study
ILS
study specifically designed to estimate the repeatability and reproducibility of a standard test method achieved
at a fixed point in time by multiple laboratories through the statistical analysis of their test results obtained on
aliquots prepared from multiple materials
3.10
known value
quantitative value for a property that can be theoretically derived or implied by the preparation of the sample
Note 1 to entry: The known value does not always exist, for example for empirical tests such as flash point.
3.11
mean
sum of a set of results divided by the number of results
3.12
mean square
sum of squares divided by the degrees of freedom
3.13
normal distribution
probability distribution of a continuous random variable, x, such that, if x is any real number, the probability
density is as shown in Formula (1):
2
11 x
f x exp , x (1)
2
2π
2
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Note 1 to entry: In the context of modelling distribution of test results, is the population mean, or true value (see 3.26) of
the property as determined by a specific test method; is the standard deviation of the normal distribution used to
describe the distribution of an infinite number of test results obtained using the same test method by an infinite of
laboratories ( 0).
3.14
operator
person who normally and regularly carries out a particular test
3.15
outlier
result far enough in magnitude from other results to be considered not a part of the set
3.16
precision
closeness of agreement between the results obtained by applying the same test procedure several times on
essentially the same materials and under prescribed conditions
Note 1 to entry: The smaller the random part of the experimental error, the more precise is the procedure.
3.17
random error
component of measurement error that in replicate measurements varies in an unpredictable manner
3.18
repeatability
qualitatively closeness of agreement between independent results obtained in the normal and correct
operation of the same method on essentially the same test material, in a short interval of time, and under the
same test conditions (same operator, same apparatus, same calibration, same laboratory) that varies as
random error
NOTE 1 to entry: The representative parameters of the dispersion of the population that can be associated with the results
are qualified by the term “repeatability”, for example, repeatability standard deviation or repeatability variance. It is
important that the term “repeatability” not be confused with the terms “between repeats” or “repeats” when used in this way
(see 3.19). Repeatability refers to the state of minimum random variability of results. The period of time during which
repeated results are to be obtained should therefore be short enough to exclude time-dependent errors, for example,
variation caused by environmental changes, or variation associated with multiple calibrations.
3.19
repeatability
quantitatively value equal to or below which the absolute difference between two single test results obtained
under specified conditions can be expected to lie with a probability of 95 %
Note 1 to entry: For the details of the conditions specified, see 3.18.
3.20
reproducibility
qualitatively closeness of agreement between individual results obtained in the normal and correct operation
of the same method on essentially the same test material but under different test conditions (different
operators, different apparatus, different calibrations, and different laboratories) that varies as random error
Note 1 to entry: The representative parameters of the dispersion of the population that can be associated with the results
are qualified by the term “reproducibility”, for example, reproducibility standard deviation or reproducibility variance.
3.21
reproducibility
quantitatively value equal to or below which the absolute difference between two single test results obtained
under specified conditions that can be expected to lie with a probability of 95 %
Note 1 to entry: For the details of the conditions specified, see 3.20.
3
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3.22
result
final value obtained by following the complete set of instructions in a test method; it may be obtained from a
single determination or from several determinations depending on the instructions in the method
Note 1 to entry: It is assumed that the result is rounded off according to the procedure specified in Annex G.
3.23
standard deviation
measure of the dispersion of a series of results around their mean, equal to the positive square root of the
variance and estimated by the positive square root of the mean square
3.24
sum of squares
sum of squares of the differences between a series of results and their mean
3.25
true value
for practical purposes, the value towards which the average of single results obtained by n laboratories tends,
as n tends towards infinity
Note 1 to entry : Such a true value is associated with the particular method of test.
[11]
Note 2 to entry: A different and idealized definition is given in ISO 3534-2 .
3.26
variance
mean of the squares of the deviation of a random variable from its mean, estimated by the mean square
4 Stages in the planning of an Interlaboratory Study for the determination of the
precision of a test method
4.1 General
The stages in planning an Interlaboratory Study (ILS) are as follows:
a) preparing a draft method of test;
b) planning a pilot study with at least two laboratories;
c) planning the ILS;
d) executing the ILS.
The four stages are described in turn in 4.2 to 4.5.
4.2 Preparing a draft method of test
This shall contain all the necessary details for carrying out the test and reporting the results. Any condition that
could alter the results shall be specified.
A clause on precision is included in the draft method of the test at this stage only as a heading. It is
recommended that the lower limit of the scope of the test method is not less than the region of the lowest
value tested in the ILS, and is at least 2R greater than the lowest achieved result,
...
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