Time-series covariance and spectral noise
Research context
postgraduate concept · established · As of 2026-10-10
For N observations of one stationary process with covariance C_ij, Var(mean)=N⁻²Σ_ijC_ij.
Key knowledge
For N observations of one stationary process with covariance C_ij, Var(mean)=N⁻²Σ_ijC_ij. Positive correlations can prevent the independent-noise 1/√N improvement; drift and nonstationarity require explicit models. Allan-type stability summaries and spectral estimates characterize different time scales rather than replace systematic calibration uncertainty.
Values and equations
Var(x̄)=N⁻²Σ_iΣ_j C_ij
- x̄
- Mean signal with signal units
- C_ij
- Observation covariance; squared signal units
- N
- Observation count
Conditions and scope
- Finite second moments and declared sampling/averaging; covariance has squared signal units.
- Test stationarity and model residuals, preserve cross-time covariance through filtering, and separate shared systematic effects from random process noise.
Sources · 3
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
- Analysis of dynamic measurements (2012)Sascha Eichstädt / PTB and Technische Universität BerlinResearch paper · PDF
- JCGM GUM-6:2020 · Developing measurement modelsJoint Committee for Guides in Metrology / BIPMReference guide · PDF
- Statistical methods for next-generation clock networks (2025 project update)NIST Statistical Engineering Division and optical-clock collaboratorsResearch project overview
Evidence and review
Inspected §§1.2–1.3 and 3–4: LTI identification, Wiener/Tikhonov filters, regularization-error budget and correlated signals; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication. Inspected §§8.5, 10.4–10.6, 11.4, 11.6–11.10, 12 and Annex B: shared effects, inverse calibration, time series and prior sensitivity; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication. Inspected between-day excess scatter and hierarchical ratio-model account; project summary, not original experimental full text; source check dated 2026-10-10. Scope is limited to the cited statements, equations and assumptions, not the whole publication.
2026-10-10 · Author source inspection of the displayed claim, model assumptions and equations; independent exact-content and branch-inventory review is a separate gate. Contemporary status is a dated snapshot, not a promise of ongoing monitoring.
Entry details
Permanent link to this entry ↗- Record identity
- research-measurement-correlated-time-series
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference