To be able to judge if uncertainty has been properly expressed and reported it is important to be familiar with relevant standards for expression of uncertainty.
There exists one internationally recognized standard for expression of uncertainty:
Guide to the expression of uncertainty in measurement.
The standard is freely available.
That is the only broadly recognized guideline on the expression of uncertainty.
The following seven organizations* supported the development of that Guide, which is published in their name:
BIPM: Bureau International des Poids et Measures
IEC: International Electrotechnical Commission
IFCC: International Federation of Clinical Chemistry
ISO: International Organization for Standardization
IUPAC: International Union of Pure and Applied Chemistry
IUPAP: International Union of Pure and Applied Physics
OlML: International Organization of Legal Metrology
The intention of this post is to highlight how uncertainty should be reported – not how to calculate uncertainty. The purpose of this post is to make the reader able to recognize when uncertainty has not been reported in a proper way. If uncertainty is not reported in a proper way – the uncertainty is most likely not properly calculated and documented either. At least, there is reason to be critical – and start to ask some questions about uncertainty.
Ok – here we go:
Ref.: 7.2.3 in Guide to the expression of uncertainty …:
Simply put, the result of an estimate should be reported by:
– giving a full description of how the measurand Y is defined
– stating the result of the measurement as Y = y ± U
– give the units of y and U
– giving the approximate level of confidence associated with the interval y ± U
– state how the level of confidence was determined;
Ref.: 7.1.4 in Guide to the expression of uncertainty …:
Although in practice the amount of information necessary to document a measurement result depends on its intended use, the basic principle of what is required remains unchanged: when reporting the result of a measurement and its uncertainty, it is preferable to err on the side of providing too much information rather than too little. For example, one should
a) describe clearly the methods used to calculate the measurement result and its uncertainty from the experimental observations and input data;
b) list all uncertainty components and document fully how they were evaluated;
c) present the data analysis in such a way that each of its important steps can be readily followed and the calculation of the reported result can be independently repeated if necessary;
d) give all corrections and constants used in the analysis and their sources.
A test of the foregoing list is to ask oneself “Have I provided enough information in a sufficiently clear manner that my result can be updated in the future if new information or data become available?”
If you wonder if United Nations climate panel IPCC meet this standard, the following posts address that question:
In short – IPCC is not even close.