BlackSwan

Very unexpected and unpredictable event. So outlying that trying to account for it actually screws up your statistical model.

• http://globalguerrillas.typepad.com/globalguerrillas/2004/04/was911a_black.html

• http://www.edge.org/3rdculture/taleb04/talebindex.html

Contrast the US report on 9/11 : "The United States government was simply not active enough in combating the terrorist threat before 9/11," Mr Kean said.

He added that it had been impossible to determine whether the 11 September attacks could have been prevented - it was "possible", but this could not be borne out by facts.

http://news.bbc.co.uk/1/hi/world/americas/3916885.stm

See also :

• DanBricklin on NormalAccidents : http://www.bricklin.com/learningfromaccidents.htm