BS EN ISO 19036:2019 pdf free.Microbiology of the food chain -Estimation of measurement uncertainty for quantitative determinations.
3.1.9 measurement uncertainty MU parameter, associated with the result of a measurement, that characterizes the dispersion of the values that could reasonably be attributed to the measurand (3.1.5) Note 1 to entry: The parameter may be, for example, a standard deviation [or a given multiple of it), or the half-width of an interval having a stated level of confidence.
Note 2 to entry: Measurement uncertainty comprises, in general, many components. Some of these components may be evaluated from the statistical distribution of the results of a series of measurements and can be characterized by experimental standard deviations. The other components, which also can be characterized by standard deviations, are evaluated from assumed probability distributions based on experience or other information. Note 3 to entry: It is understood that the result of the measurement is the best estimate of the value of the measurand and that all components of uncertainty, including those arising from systematic effects, such as components associated with corrections and reference standards, contribute to the dispersion.
[SOURCE: ISO/IEC Guide 98-3:2008, 2.2.3, modified 一The preferred term has been changed from “uncertainty of measurement” to “measurement uncertainty”.] 3.1.10  standard uncertainty U uncertainty of the result of a measurement expressed as a standard deviation [SOURCE: ISO/IEC Guide 98-3:2008, 2.3.1, modified- The symbol has been added.]3.1.11 combined standard uncertainty ucUy) standard uncertainty (3.1.10]) of the result of a measurement when that result is obtained from the values of a number of other quantities, equal to the positive square root of a sum of terms, the terms being the variances or covariances of these other quantities weighted according to how the measurement result varies with changes in these quantities [SOURCE: ISO/IEC Guide 98-3:2008, 2.3.4, modified一The symbol has been added.] 3.1.12 expanded uncertainty U quantity defining an interval about the result of a measurement that may be expected to encompass a large fraction of the distribution of values that could reasonably be attributed to the measurand (3.1.5) Note 1 to entry: The fraction may be regarded as the coverage probability or level of confidence of the interval. Note 2 to entry: To associate a specific level of confidence with the interval defined by the expanded uncertainty requires explicit or implicit assumptions regarding the probability distribution characterized by the measurement result and its combined standard uncertainty (3.1.11). The level of confidence that may be attributed to this interval can be known only to the extent to which such assumptions may be justified.BS EN ISO 19036 pdf download.