Definitional uncertainty
More repetitions do not resolve an underspecified measurand.
Key knowledge
Definitional uncertainty results from the finite detail in a measurand definition. It is a component of measurement uncertainty and gives a minimum uncertainty achievable under that definition. A length measurand without adequately specified endpoints or relevant thermal state can retain ambiguity even if indication noise is reduced by repetition. Refining the definition can change that component and may change the quantity being measured.
Conditions and scope
- The minimum is conditional on the stated measurand definition; it is not a universal quantum or instrumental lower bound.
- The illustrative length ambiguity must be assessed for the actual object and intended use; do not assign it a universal probability distribution.
Sources · 1
References
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Evidence and review
Read VIM2.27 definition and notes on the minimum achievable uncertainty and dependence on descriptive detail. The endpoint/thermal example and averaging limitation are disclosed applications of the existing measurand/noise distinction.
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