How is measurement uncertainty calculated and reported?

Measurement uncertainty analysis follows GUM (Guide to the Expression of Uncertainty in Measurement). Process: identify uncertainty sources, quantify each component as standard uncertainty (Type A from statistics, Type B from specifications/judgment), combine using root-sum-square (assuming independence), apply sensitivity coefficients for different units, and expand with coverage factor k (k=2 for 95% confidence). Report as: value +/- expanded uncertainty with coverage factor. Uncertainty budget documents each contribution. Dominant sources guide improvement efforts. Traceability requires uncertainty chain back to national standards.