PRIORITY business intelligence

The general requirements that testing and calibration laboratories have to meet if they wish to demonstrate that they operate to a quality system, are technically competent and are able to generate technically valid results are contained within ISO/IEC 17025:2005. One of the main requirements of the ISO/IEC 17025:2005 is the estimation of measurement uncertainty.

Moreover, in order to utilise a result to decide whether it indicates compliance or non-compliance with a specification, it is necessary to take into account the measurement uncertainty.

Possible sources of uncertainty in an analytical procedure may be identified during:

• Sampling
• Sample preparation
• Presentation of Certified Reference Materials to the measuring system
• Calibration of Instrument
• Analysis (data acquisition)
• Data processing
• Presentation of results
• Interpretation of results

In estimating the overall uncertainty, it may be necessary to take each source of uncertainty and treat it

separately to obtain the contribution from that source. Each of the separate contributions to uncertainty is referred to as an uncertainty component.

The total uncertainty, termed combined standard uncertainty is obtained by combining all the uncertainty components, however evaluated, using the law of propagation of uncertainty.

For most purposes an expanded uncertainty, should be used. The expanded uncertainty provides an interval within which the value of the measurand is believed to lie with a higher level of confidence.