Abstract
In the world of measurement, such terms as "error" or "precision" have been used to express the reliability of a measuring system. But these terms have not been clearly defined. Recently, a guideline entitled "A Guide to the Expression of Uncertainty in Measurement" was published by ISO for the purpose of internationally unifying the expression. The term "uncertainty," which indicates the reliability of a measuring system, is very important when discussing about the traceability of measurement standards. In quality Engineering, the SN ratio has been used as a scale of measurement error. In this paper, it was discussed in conjunction with uncertainty in measurement.