2.
Measurement Process Characterization
2.5. Uncertainty analysis


Definition of standard uncertainty 
The sensitivity coefficients and standard deviations are combined by
root sum of squares to obtain a 'standard uncertainty'. Given
R components, the standard uncertainty is:


Expanded uncertainty assures a high level of confidence 
If the purpose of the uncertainty statement is to provide coverage
with a high level of confidence, an expanded uncertainty is
computed as
where k is chosen to be the t_{1α/2,ν} critical value from the ttable with ν degrees of freedom. For large degrees of freedom, k = 2 approximates 95 % coverage. 

Interpretation of uncertainty statement 
The expanded uncertainty defined above is assumed to provide a
high level of coverage for the unknown true value of the measurement
of interest so that for any measurement result, Y,
