About not Correcting for Systematic Effects

In practice, measurement results are sometimes described by an estimate, which is not the best one as defined in the GUM. Such alternative estimates arise when the result of a measurement is not corrected for all systematic effects. No recommendation exists in the GUM for associating an uncertainty with an uncorrected estimate.

A common choice in guidelines and in the literature is the uncertainty u(y′)=u2(y)+(y-y′)2u\left( {y'} \right) = \sqrt {{u^2}\left( y \right) + {{\left( {y - y'} \right)}^2}} for an alternative estimate y′. It arises from the expected quadratic loss, on which, also in the GUM, the standard uncertainty u(y), and the best estimate y are based. However, such an uncertainty is not a standard uncertainty and we establish, it may not be used for uncertainty propagation.

One consequence is, for example, that pairs (y′, u(y′)) are not to be used in calibration certificates.