"The problem of averaging data containing discrepant values is nicely discussed in Ref. x [...] It is difficult to develop a procedure that handles simultaneously in a reasonable way two basic types of situations: (a) data that lie apart from the main body of the data are incorrect (contain unreported errors); and (b) the opposite -itis the main body of data that is incorrect. Unfortunately, as Ref. x shows, case (b) is not infrequent [...] the choice of procedure is less significant than the initial choice of data to include or exclude."
The Review of Particle Properties 2004, p.16.