Insufficient data

 I heard this joke spoken at an international insurance conference 40 years ago.

China had just opened up. A train was travelling in Inner Mongolia.

Three foreigners, who were visiting in China for the first time, looked out of the window and saw a lone sheep, black in color, in the distance.

A foreigner, who is a journalist, said "All sheep in Mongolia are black".

The second foreigner, who is an engineer, said "Sorry. There is one sheep in Mongolia that is black".

The third foreigner, who is an actuary, said, "To be exact, there is at least one sheep in Mongolia that is black, at least on one side".

I share this story to advise people not to make conclusions based on insufficient data.