Marginally detectable bias (MDB)
The minimum size of gross error in an observation that may be detected with given probabilities of type 1 and type 2 errors. A type 1 error occurs when an observation without a gross error is wrongly rejected, and a type 2 error occurs when an observation with a gross error is wrongly accepted.
Source: Nick Ward, Vicechair, IALA e-Nav Committee, March 2009
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM