Physicists measure significance of their results in units of standard deviation, σ.
3σ is called an “evidence” – a very interesting case, but it happened already in the history of particle physics that the results with this significance was not confirmed later.
5σ is called an “observation”: ATLAS and CMS have reached this significance for their Hiiggs boson like particle “observation” on 4th July, 2012.
8σ is much much more significant. Both ATLAS and CMS have not yet (February 2013) reached this level of significance for their Higgs boson like particle “observation”.