Uncertainty of measurement: implications of its use in analytical science

Abstract

The uncertainty of a measurement is the interval on the measurement scale within which the true value lies with a specified probability, when all sources of error have been taken into account. The proposed widespread use of uncertainty in metrology represents an important new paradigm in the area of the quality of measurements. Increasingly, analytical chemists will be expected as standard practice to provide (or include implicitly) a statement of the uncertainty alongside their estimate of a measurand. Indeed, a measurement cannot be properly interpreted without knowledge of its uncertainty. Such use of uncertainties will have a profound influence on many aspects of analytical chemistry, and current concepts and practices relating to the quality of data will have to be revised. As a result uncertainty of measurement will become the main unifying principle in data quality. This paper makes a brief review of the concepts and practices of data quality in analytical chemistry in relation to uncertainty. It is addressed primarily to the bodies that will be responsible for the introduction of uncertainty into routine practice. It is an attempt to ensure from the outset that a consistent approach will be applied throughout the field of data quality in a manner that is usable by and acceptable to the whole analytical community. Consequently, the paper deals only with the general principles of the subject, and there will be many details that have to be considered subsequently. The paper does not address the incorporation in interpreted data of uncertainty arising from that interpretation.