Once in 50 years, wait, whats the standard deviation and the mean? Just so i can calculate the probabilty..

http://www.straitstimes.com/Breaking+News/Singapore/Story/STIStory_457298.html

Deluge was a 'freak' event
Nov 21, 2009
By Amresh Gunasingham & Ang Yiying

THURSDAY'S deluge which submerged parts of Bukit Timah was a 'freak' event that occurs once in 50 years, Minister for the Environment and Water Resources Yaacob Ibrahim said on Friday.

http://www.wildsingapore.com/news/20061112/061220-1.htm#cna3

Channel News Asia, 21 Dec 2006
Businesses along East Coast suffering due to rain
By Valarie Tan

At Upper Seletar Reservoir, excess water was released into the sea by opening the tide gates.

Dr Yaacob Ibrahim, Environment and Water Resources Minister, says: "You can't design for rainfall of this level, it is just too huge. The thing we can accept is that we can only design our canal of a certain size, and at the end of the day, we have to live with some of these occurrences which occur once in 50 years or so.

Time Flies. 50 years in a blink.