Glossary¶

Alphabetical overview of the technical terms used in ConCertainty and in measurement uncertainty determination.

B¶

Bias Systematic deviation of one's own measured values from the certified reference value of a standard or reference material. A bias indicates that the measurement is precise but not accurate. The bias enters the measurement uncertainty via the contribution to comparability.

D¶

D_rms,rel Root mean square of the relative deviations of one's own measured values from the consensus value across all selected proficiency test participations for a parameter. Displayed in ConCertainty in the detail view of the calculation results for the proficiency test method.

Data basis In ConCertainty, the totality of the recorded measurement series and proficiency test participations on the basis of which the measurement uncertainty is calculated.

E¶

Coverage factor k A factor by which the combined measurement uncertainty is multiplied to obtain the expanded measurement uncertainty. The k-factor determines the confidence level: k = 2 corresponds to approx. 95.45 %, k = 3 corresponds to approx. 99.73 %.

Expanded measurement uncertainty (U) The combined measurement uncertainty multiplied by the coverage factor k. It specifies an interval within which the true value lies with a defined probability. At k = 2, this corresponds to a confidence level of approx. 95.45 %.

G¶

GUM Guide to the Expression of Uncertainty in Measurement. The fundamental international document for determining and stating measurement uncertainties. Published by BIPM, IEC, IFCC, ILAC, ISO, IUPAC, IUPAP, and OIML.

K¶

k-factor See Coverage factor k.

Identifier A technical designator that uniquely identifies a master data entry in ConCertainty. Identifiers consist of lowercase letters, digits, and hyphens; the only exception are PSE elements, whose identifier corresponds to the chemical symbol (e.g. Si). Once an entry has been saved, the identifier is immutable.

L¶

Laboratory sample The physical sample on which measurements are performed. In ConCertainty, a material is assigned to a laboratory sample. Depending on whether certificate data is stored, the sample is available as a basis for reproducibility, comparability, or both.

M¶

Material A specific manifestation within a matrix – e.g. a particular alloy, a type of water, or a type of oil. Materials are maintained in the detail view of a matrix.

Matrix The sample material as a superordinate category in ConCertainty – e.g. aluminum, water, or oil. A matrix combines all associated materials.

P¶

Parameter A measured quantity that can be determined in a test profile – e.g. silicon, fluoride, or pH value. In ConCertainty, there are system-maintained PSE elements and user-defined parameters.

Test profile A combination of test method, matrix, and a list of parameters with associated units. The test profile is the central unit to which measurement series and evaluations refer.

R¶

Reference material (RM) A sample with documented reference values, to which one's own measured values can be made traceable. Created in ConCertainty as a laboratory sample with certificate data.

Reproducibility The ability to achieve consistent measurement results under repeatability conditions. In ConCertainty, reproducibility enters the measurement uncertainty calculation as u_R,w.

Proficiency test An organized comparison program in which several laboratories analyze the same sample and submit their results to an organizer. The organizer evaluates all submissions and provides each laboratory with an evaluation report.

Traceability The property of a measured value that allows it to be related to a recognized reference value via an unbroken chain of comparison measurements. In ConCertainty, measurement series on laboratory samples with stored certificate data are considered traceable – they can be included as a contribution to comparability in the measurement uncertainty calculation.

S¶

Standard Synonym for reference material or certified reference material. A sample with known, documented reference values.

U¶

u_b,rel Relative contribution of comparability to the measurement uncertainty.

u_Cref,rel Relative contribution of the uncertainty of the consensus value to comparability. Displayed in ConCertainty in the detail view of the calculation results for the proficiency test method.

u_c,rel Relative combined measurement uncertainty. Composed of u_R,w and u_b,rel.

u_R,w Relative contribution of reproducibility to the measurement uncertainty.

U_rel Relative expanded measurement uncertainty. Results from u_c,rel multiplied by the coverage factor k.

V¶

Comparability The agreement of one's own measured values with an external reference value. In ConCertainty, comparability enters the measurement uncertainty calculation as u_b,rel – either based on measurement series on laboratory samples with certificate data (reference material method) or based on recorded proficiency test participations (proficiency test method).

Reproducibility standard deviation (s_R,i) The standard deviation of the participants' results for a parameter, as specified by the organizer of a proficiency test. Entered in ConCertainty when recording proficiency test participations.

Confidence level The probability with which the true measured value lies within the interval defined by the expanded measurement uncertainty. A confidence level of 95.45 % corresponds to a coverage factor of k = 2.

Z¶

Certified reference material (CRM) A reference material whose properties are documented by a certificate issued by an accredited body. In ConCertainty, a CRM is created as a laboratory sample with stored certificate data.