Reaffirmed 2022

NATIONAL FOREWORD

This Indian Standard (First Revision) which is identical with ISO 21748 : 2017 ‘Guidance for the use of repeatability, reproducibility and trueness estimates in measurement uncertainty evaluation’ issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on recommendation of the Statistical Methods for Quality and Reliability Sectional Committee and approval of the Management and Systems Division Council.

This standard was originally published in 2014 and was identical with ISO 21748 : 2010. The first revision of this standard has been undertaken to align it with the latest version of ISO 21748 : 2017.

The major changes in this revision are as follows:

a) Minor change in the title (estimation to evaluation) to reflect preferred use of terms (see third list item);

b) Minor changes in wording and format to conform to current ISO Directives, which included the addition of Clause 2 and renumbering of subsequent clauses;

c) The phrases ‘estimation of measurement uncertainty’ (and similar usage of ‘estimate’) and ‘evaluation of measurement uncertainty’ (and similar usage of ‘evaluate’) have been amended to distinguish quantitative estimates of the components of uncertainty from the process of evaluations of measurement uncertainty, which can include additional relevant considerations;

d) The word ‘standard’ has been added before ‘uncertainty’ where appropriate, for clarity;

e) Redundant definitions of terms defined as squared quantities, where the standard deviation was also defined [s2b, s2inh, s2L, s2r, s2W, u2(y), s2L, s2r] have been removed;

f) In the definition of rij, ‘in the interval -1 to +1’ was removed;

g) In the definition of the term sinh, ‘uncertainty’ was changed to ‘standard deviation’;

h) In the definitions for u(y), ui(y) and u(Y), U(y), equations were removed (not necessary for standard terms);

j) The symbols from all definitions of terms where they had been included (combined standard uncertainty, coverage factor, expanded uncertainty, standard uncertainty) have been removed;

k) The definition of y0 has been removed because the term is not used in the document;

m) In 7.4, first dash, ‘quality control charts’ has been replaced with ‘control charts’;

n) A note has been added to Clause 10 (previously Clause 9);

p) In 13.1, 14.1 and 14.3 (previously 12.1, 13.1 and 13.3), ‘combined’ has been added before ‘standard uncertainty’;

q) In 13.2.1 and 13.2.2 (previously 12.2.1 and 12.2.2), the word ‘combined’ has been removed before ‘expanded uncertainty’;

r) In A-1, changed italics ‘standard uncertainties’ to standard text;

s) In A-1, 7th paragraph (3rd from end), ‘combined standard uncertainties [u(xi)]’ has been changed to ‘additional standard uncertainties u(y)’;

t) In C-3, title, ‘Uncertainty for AOAC method 990.12’ has been replaced with ‘Uncertainty for measurements obtained by AOAC method 990.12’;

u) In C-3.2, ‘eight laboratories’ has been replaced with ‘twelve laboratories’;

v) In C-4.4, ‘0,07 g/kg (0,7 percent as mass fraction)’ has been changed to ‘7 g/kg (0,7 percent as mass fraction)’; and

w) References [27] and [28] have been updated.

The text of ISO Standard has been approved as suitable for publication as an Indian Standard without deviations. Certain terminologies and conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’.

b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a point (.) as the decimal marker.