2.
Measurement Process Characterization
2.5. Uncertainty analysis 2.5.5. Propagation of error considerations


Case: Y=f(X,Z) 
Standard deviations of reported values that are functions of
measurements on two variables are reproduced from a paper by H. Ku
(Ku).
The reported value, Y is a function of averages of N measurements on two variables. 
and are averages of N measurements 
= standard dev of X;
Note: Covariance term is to be included only if there is a reliable estimate 
Note: this is an approximation. The exact result could be obtained starting from the exact formula for the standard deviation of a product derived by Goodman (1960). 