Uncertainty: Only One Mathematical Approach to Its Evaluation and Expression?

This paper considers the well-known concept of uncertainty of a measurement result and discusses the mathematical approach adopted for its evaluation and expression by the present standard documents and, in particular, the Guide to the Expression of Uncertainty in Measurement. The practical limitations introduced by the assumptions of this mathematical approach are discussed, and the requirements of a new mathematical approach capable of overcoming the present limitations are drawn. A different mathematical approach, based on the theory of evidence and originally developed by the authors in recent years, is presented and discussed, with some new findings and observations.