What is measurement uncertainty?
Every measurement result is meaningful only together with an interval within which the true value lies. Our laboratory estimates the measurement uncertainty for every test method within the scope of accreditation; the expanded uncertainty is stated with a coverage factor of k=2 (a confidence level of approximately 95%).
Uncertainty components
The calibration uncertainty, resolution and stability of the equipment; repeatability; environmental conditions; and effects arising from the sample, the operator and the method are evaluated.
Decision rules
| Rule | Meaning |
|---|---|
| Simple acceptance (binary statement) | If the measured value is within the specification limit, it conforms; if outside, it does not conform. |
| Guarded acceptance | For a statement of conformity, the measured value must lie inside the limit by at least the expanded uncertainty. |
| Guarded rejection | For a statement of non-conformity, the measured value must lie outside the limit by at least the expanded uncertainty. |
| No statement | Only the measurement result and its uncertainty are reported; no statement of conformity is given. |
Default rule
If the product standard or legislation specifies a decision rule, that rule is applied. If not, and no other agreement has been made with you, simple acceptance is applied. The decision rule is explained to you before the contract, and the rule applied is clearly stated in the report. If, because of the uncertainty band, the measured value falls within the zone where no decision can be made, this is also stated in the report.