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BS ISO 5725-2:2019

BS ISO 5725-2:2019

$215.11

Accuracy (trueness and precision) of measurement methods and results – Basic method for the determination of repeatability and reproducibility of a standard measurement method

Published By Publication Date Number of Pages
BSI 2019 78
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1.1

This document

  • amplifies the general principles for designing experiments for the numerical estimation of the precision of measurement methods by means of a collaborative interlaboratory experiment;

  • provides a detailed practical description of the basic method for routine use in estimating the precision of measurement methods;

  • provides guidance to all personnel concerned with designing, performing or analysing the results of the tests for estimating precision.

NOTE Modifications to this basic method for particular purposes are given in other parts of ISO 5725.

1.2

It is concerned exclusively with measurement methods which yield measurements on a continuous scale and give a single value as the test result, although this single value can be the outcome of a calculation from a set of observations.

1.3

It assumes that in the design and performance of the precision experiment, all the principles as laid down in ISO 5725-1 are observed. The basic method uses the same number of test results in each laboratory, with each laboratory analysing the same levels of test sample; i.e. a balanced uniform-level experiment. The basic method applies to procedures that have been standardized and are in regular use in a number of laboratories.

1.4

The statistical model of ISO 5725-1:1994, Clause 5, is accepted as a suitable basis for the interpretation and analysis of the test results, the distribution of which is approximately normal.

1.5

The basic method, as described in this document, (usually) estimates the precision of a measurement method:

  1. when it is required to determine the repeatability and reproducibility standard deviations as defined in ISO 5725-1;

  2. when the materials to be used are homogeneous, or when the effects of heterogeneity can be included in the precision values; and

  3. when the use of a balanced uniform-level layout is acceptable.

1.6

The same approach can be used to make a preliminary estimate of precision for measurement methods which have not reached standardization or are not in routine use.

PDF Catalog

PDF Pages PDF Title
2 undefined
7 Foreword
8 Introduction
9 1 Scope
10 2 Normative references
3 Terms and definitions
4 Symbols
12 5 Estimates of the parameters in the basic model
13 6 Requirements for a precision experiment
6.1 Layout of the experiment
14 6.2 Recruitment of the laboratories
6.3 Preparation of the materials
15 7 Personnel involved in a precision experiment
7.1 Panel
16 7.2 Statistical functions
7.3 Executive functions
17 7.4 Supervisors
18 7.5 Operators
8 Statistical analysis of a precision experiment
8.1 Preliminary considerations
19 8.2 Tabulation of the results and notation used
8.2.1 Cells
8.2.2 Redundant data
8.2.3 Missing data
8.2.4 Outliers
8.2.5 Outlying laboratories
8.2.6 Erroneous data
8.2.7 Balanced uniform-level test results
20 8.2.8 Collation of data and intermediate values
8.2.9 Original test results
8.2.10 Cell means (Form B of Figure 2)
8.2.11 Measures of cell spread (Form C of Figure 2)
21 8.2.12 Corrected or rejected data
8.3 Scrutiny of results for consistency and outliers
8.3.1 Approaches for scrutiny of data
8.3.2 Graphical consistency technique
24 8.3.3 Numerical outlier technique
8.3.4 Cochran’s test
26 8.3.5 Grubbs’ tests
28 8.3.6 Repeated testing for outlying means or outlying data points
8.3.7 Alternative outlier inspection and test methods
8.4 Calculation of the general mean and variances
8.4.1 Method of analysis
29 8.4.2 Basic data
8.4.3 Non-empty cells
8.4.4 Calculation of the general mean, 
8.4.5 Calculation of variances
30 8.4.6 Alternative calculation methods for variances
31 8.4.7 Dependence of the variances upon m
8.5 Establishing a functional relationship between precision values, s, and the mean level, m
8.5.1 Choice of functional relationship
32 8.5.2 Fitting relationships I and II
33 8.5.3 Fitting relationship III
34 8.5.4 Fitting relationship IV
36 8.6 Statistical analysis as a step-by-step procedure
38 8.7 Report to the panel and decisions to be taken by the panel
8.7.1 Report by the statistical expert
40 8.7.2 Decisions to be taken by the panel
41 8.7.3 Full report
9 Statistical tables
46 Annex A (informative) Number of laboratories required for an estimate of precision
49 Annex B (informative) Alternative calculations of variance components
52 Annex C (informative) Examples of the statistical analysis of precision experiments
74 Annex D (informative) Calculation of critical values and indicators
77 Bibliography

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BS ISO 5725-2:2019
$215.11