I feel this is an appropriate place to tell the following quite well-known joke:

There was a train going north from England into Scotland, and in it were a Statistician, a Physicist and a Mathematician. Just after they passed the border into Scotland (with a sign up saying `You are now Entering Scotland') they looked out of the window and saw a black sheep in a field.

`Aha!' said the Statistician. `All Scottish Sheep are black.'

`Oh no', said the Physicist. `SOME Scottish sheep are black. Isn't that so?', turning to the Mathematician.

`I fear, gentlemen', said the Mathematician, `that you both go far beyond the data. All that can be said, and that with grave reservations, is that there exists in Scotland a field, in which there exists a sheep, AT LEAST ONE SIDE OF WHICH IS BLACK'.