Probably a discovery: Bad mathematics means rough scientific communication

According to the media, in spring of this year the experiment CDF at Fermilab has made most likely ("this result has a 99.7 percent chance of being correct", Discovery News) a great discovery ("the most significant in physics in half a century", NYT). However, since the very beginning, practically all particle physics experts did not believe that was the case. This is the last of a quite long series of fake claims based on trivial mistakes in the probabilistic reasoning. The main purpose of this note is to invite everybody, but especially journalists and general public, most times innocent victims of misinformation of this kind, to mistrust claims not explicitly reported in terms of how much we should believe something, under well stated conditions and assumptions. (A last minute appendix has been added, with comments on the recent news concerning the Higgs at LHC.)