The BBC reported last week that evidence for the Higgs Boson is “around the two-sigma level of certainty” and provides further explanation:
Particle physics has an accepted definition for a "discovery": a five-sigma level of certainty. The number of standard deviations, or sigmas, is a measure of how unlikely it is that an experimental result is simply down to chance rather than a real effect”
This is nice and clear, but it is also wrong, as we have pointed out before in a previous blog by Kevin McConway.