A physicist, an engineer and a statistician go out hunting.
Presently, they find a deer. The physicist draws up complex ballistics calculations to work out where to shoot, but as he’s assumed it’s a spherical deer in a vacuum, his shot is two metres too low.
The engineer jury-rigs a fix for the equation to take air resistance into account and allows a bit extra ‘just in case’, so his shot is two metres too high.
The statistician shouts, “we got him!”