How reliable is my uncertainty estimate?

Abstract

It has become accepted practice for laboratories to report the value of the uncertainty of each measured quantity value (i.e. measurement uncertainty, MU). Informally, the MU expresses the range of values within which the true value of the analyte concentration (i.e. the value of the measurand) is asserted to lie. It is much less widely appreciated that the estimate of MU is also not an exact or ‘true’ value. The quoted MU is actually only an estimate, and has its own uncertainty which also can be expressed using a confidence interval (CI) for a specified confidence level (e.g. 95%).