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A measure of confidence - How standards build trust in weights and measures

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Metrology, standards, and accreditation are three fundamental elements that can open the door to the global market, and to the benefits that come to those countries and industries that participate.

This article looks at how standards promote fairness and accuracy in weights and measures, and how they enable global trade to flourish.

Societies are built on trade, and trade relies on accurate measurements. Fair weights and measures have been fundamental to business and commerce since ancient times. Artifacts for measuring weight and length can be found in archeological sites dating back more than 5 000 years. The Treaty of the Metre in 1875 is one of the earliest multinational agreements, and perhaps the oldest international treaty still in effect. Today’s International Standards bring metrology – the science of measurement – up to date, and help create confidence in products and services.
Can we be sure ?

When we buy a product we think it will meet our needs, but how can we be sure that it will fulfill expectations ? We could purchase from a supplier we have used before, follow a recommendation from a friend, or see what a successful competitor uses. However, in an increasingly complex global market we can’t always buy from the same vendor, or rely on recommendations. We might have to buy from a different source if we want a better product or service, or a lower price. And therein lies the risk.

If we have specifications – for example, a detailed description of the diameter of a bolt, the chemical content of an oil, the strength of concrete, or the additives in food – then we have a good chance of selecting exactly the product we need.

Specifications enable us to purchase from a larger market, and provide the framework for innovation in design and manufacture. However, for this to happen, we must trust the measurements that tell us the product conforms to our specification. Thus we need metrology standards to promote accuracy, reliability, and trust in the measurement of physical, chemical and biological properties.
Measuring almost anything

Procedures to measure the properties of almost anything from raw materials to finished products are usually first described in the technical literature for that specific field of metrology. When multiple measurement techniques exist, standards are required. These are often developed and disseminated by national metrology institutes (NMIs), by other consensus standards development organizations, or by technical committees (TCs) in ISO.

Several specialized ISO committees provide the fundamental consensus-based International Standards that support other technical standards. These include two “horizontal committees” that write standards for all ISO/TCs to follow where appropriate :

    - ISO/TC 176, Quality management and quality assurance
    - ISO/TC 69, Applications of statistical methods.

ISO’s standards addressing quality management must include the principles outlined in the work of ISO/TC 176. Similarly, ISO standards using statistical methods must follow the appropriate standards developed by ISO/TC 69 (e.g. measurement of physical, chemical, and biological properties).
Trust in measurements

Common standards are required for statistical methods because most measurement procedures are not exact – repeating a measurement of the same product, at the same time, with the same technician and equipment will often produce a different result. Varying the measurement equipment, time or technician will usually increase variability, and results from a different laboratory or measurement procedure can vary even more.

Statisticians call these conditions repeatability, intermediate precision and reproducibility, respectively, and together they represent different sources of measurement uncertainty. So how can there be trust in such measurements?

To have confidence in measurement results, the capabilities of the procedures must be fully described so that metrologists (and their customers) can determine if they are sufficiently accurate. Variability in measurement results will often follow statistical principles.

The statistical standards from ISO/TC 69 that relate to measurements are developed primarily by ISO/TC 69 subcommittee SC 6, Measurement methods and results, and cover procedures for accuracy of measurement, capability of detection, measurement uncertainty, and proficiency testing. Other statistical standards from ISO/TC 69 relating to metrology are developed by subcommittees on acceptance sampling, process capability and terminology.
Confidence grows

Confidence also grows from trust that measurements are conducted by competent individuals and organizations. Most measurement procedures are extremely complex, and, in the global market, are conducted in different countries under vastly different legal systems and cultural norms. How can we trust such measurements ? Should we develop redundant testing processes in importing and exporting countries? But this only adds cost, delays product delivery, and can lead to conflicting conclusions on whether a product conforms to specification or not.

Standards for competence in conformity assessment are developed by the ISO Committee on conformity assessment (ISO/CASCO), and cover testing and calibration laboratories, inspection and certification bodies, and proficiency testing. The ISO Committee on reference materials (ISO/REMCO) develops similar standards for the competence of reference material producers. All ISO/CASCO and ISO/REMCO standards include requirements for quality management systems developed by ISO/TC 176.
Global trust

The last link in the chain of trust comes from accreditation – independent third party attestation of the competence of conformity assessment bodies – to ensure that ISO and other measurement standards are correctly followed. You can have confidence in accreditation because ISO International Standards come under rigorous surveillance by the International Laboratory Accreditation Cooperation (ILAC) and the International Accreditation Forum (IAF). ILAC members offer accreditation of metrological activities, and IAF members offer accreditation of certification activities.

Both organizations have developed policies and stringent peer review procedures that allow mutual recognition agreements for accreditations within their respective organizations. ILAC and IAF have also built an extensive network of agreements with various stakeholder organizations, including national regulatory bodies, to build trust and avoid the cost of multiple accreditations. ISO/CASCO also developed the International Standard for accreditation bodies that accredit conformity assessment organizations.

Global trust in products and services is built on International Standards for metrology and accreditation, as practised by responsible organizations dedicated to their development and application.

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