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Chapter: 8 Introduction to quality assurance of measurements
    Section: 8.1 The approach to quality

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8.1 The approach to quality

Measurements, whether biological, chemical or physical in nature, affect all aspects of our lives. They are made for a vast variety of reasons ranging from the control of an industrial process through protection of our health or the environment to enforcement of a law or regulation. In all of these applications one aspect of measurements is paramount: they need to be reliable. Furthermore, their reliability must be readily and widely accepted by those who use measurement data: the measurements need to be credible. This can be achieved through a combination of sound measurement science, adherence to quality assurance principles and the implementation of a quality system, supported where appropriate by independent, external assessment of the quality system and its application.

What do we mean by "quality" and "quality system"? Quality is often taken as synonymous with excellence and certainly scientific excellence is an important element of the quality of many measurements. A more pragmatic, and useful, concept is one of "fitness for purpose" or "satisfying the customer's need". Using this approach quality is seen to require a trade-off between excellence, cost and time. This requirement will be familiar to almost all those concerned with making measurements. It is important to set out the formal requirement for a specific measurement and the combination of the contributing factors which will best achieve it, preferably in the form of a written specification. Having prepared a specification, and where appropriate agreed it with a customer or internal client, it is essential to achieve it, not just once but for all of the measurements to be made. It is also important that those who use the data, either now or in the future, are aware of any inherent limitations imposed by the specification. A quality system aims to facilitate and ensure achievement of these goals by setting out all the necessary activities in a set of written procedures or protocols.

This chapter gives a brief overview of quality assurance principles and the implementation of quality systems. It is important to reiterate, however, that reliable measurements which are fit for their intended purpose cannot be achieved through a well-documented quality system alone. In preparing a quality manual, many organisations choose to quote John Ruskin (1819-1900):

"Quality is never an accident. It is always the result of intelligent effort. There must be a will to produce a superior thing."

His words remain true today but quoting them is not enough: the quality system will only achieve its aims if everyone within the organisation, from the most senior manager down, does indeed have the will to achieve a quality product or service. Thus it is up to managers to avoid inappropriate economies, to ensure that their personnel are motivated, understand and value their work, are suitably qualified and competent, have the right tools and working environment, and apply good measurement science. This is true regardless of whether the measurements are made for a mundane application or at the highest metrological level.

A quality system does not come for free. Most organisations will need to undertake substantial extra work to implement an appropriate system and will also incur additional on-going costs. It is frequently estimated that overall operational costs of a typical measurement laboratory may increase by 10-20% on introduction of a quality system. The "cost of quality" falls into four main areas:

  • activities necessary to prevent unreliable data from being generated;
  • activities required to monitor the quality of the data;
  • the cost of repeating measurements found to be unreliable;
  • the cost of developing and maintaining the quality system itself (including, where appropriate, external assessment or auditing).

The goal of the quality system should be to prevent errors rather than to find them. Hence the cost of repeating unreliable measurements should, ideally, be minimal if the system is working as intended. Indeed, the reduction of correction costs is widely recognised as a benefit which can be offset against the cost of the system. There are also other benefits which are important but less tangible. They include the costs of faulty products or wrong decisions which may be a consequence of unreliable data. Others relate to the ability of an organisation to win or retain customers, its image or credibility, and staff morale.

In recent years, a formal quality system has become an essential requirement for most measurement laboratories or facilities but it is not something which can be left to the measurement scientists. Implementing a quality system requires management commitment to develop and resource a quality assurance programme. This embraces a variety of activities to ensure the product is reliable in the first place, specific quality control measures to monitor product quality on a routine basis, and ongoing assessment of the satisfactory implementation of the quality assurance programme. There is a common fallacy that the quality system is synonymous with its documentation. Some of the most important elements of a quality assurance programme are described in the remainder of this article and it can be seen that they embrace far more than documentation of the laboratory's procedures. Good documentation is a key feature of an effective quality system and its preparation frequently appears to be the major burden of implementing a new quality assurance programme. It cannot be emphasized too strongly, however, that the existence of the documentation, no matter how extensive, does not guarantee reliable measurements. This can only be achieved by establishing an effective quality assurance programme and ensuring that it is applied carefully and sensibly on a daily basis by everyone involved in the work.

M. Sargent

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