Expanded uncertainty and coverage
A coverage factor scales standard uncertainty to a reported interval.
Key knowledge
Expanded uncertainty is U = k u_c. Reporting y ± U requires the factor k, intended coverage and how that coverage was obtained; k = 2 does not universally guarantee 95% coverage.
Values and equations
U = k u_c; reported interval [y − U, y + U]
- U, u_c
- Expanded and combined standard uncertainty; same unit as measurand
- y
- Measurand estimate; its physical unit
- k
- Dimensionless coverage factor
Conditions and scope
- Use a justified output distribution and, where relevant, effective degrees of freedom.
- Asymmetric output distributions may be better reported with an explicitly calculated coverage interval.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Sections 6.1–6.4: scaling, conditional normal approximation and distribution dependence.
2026-10-10 · Expanded-uncertainty reporting only; institutional k = 2 policy is not treated as a universal probability theorem.
Entry details
Permanent link to this entry ↗- Record identity
- measurement-expanded-uncertainty
- Revision
- university-reference.1
- Structured reference record
- University reference · University core expansion