Three professors (a physicist, a chemist, and a statistician) are called in to see their dean.
Just as they arrive the dean is called out of his office, leaving the three professors there.
The professors see with alarm that there is a fire in the wastebasket.
The physicist says, "I know what to do! We must cool down the materials until their temperature is lower than the ignition temperature and then the fire will go out."
The chemist says, "No! No! I know what to do! We must cut off the supply of oxygen so that the fire will go out due to lack of one of the reactants."
While the physicist and chemist debate what course to take, they both are alarmed to see the statistician running around the room starting other fires.
They both scream, "What are you doing?!?"
"Trying to get an adequate sample size!"
It was a dark winter night, and among the usual queue of studded leather, chained piercings and rubber appendages, the S&M club's bouncer was surprised to see a man in an expensive suit and tie standing patiently, a calculator in one hand.
"Sir, are you lost?" asked the doorman.
"Oh, I'm the statistician." came the reply.
"Then, what are you here for?"
With an unsettling grin, the statistician pulls out a knife.
"Oh, just standard deviation."