A physicist, a chemist, and a statistician see a fire burning across a hall in a trashcan
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 they are debating they see the statistician running around the hall and starting other fires in all the trash cans.
They both shout, “What are you doing?”
The statistician replies, “I’m just trying to get an adequate sample size guys”.