Introduction There is a telling joke sometimes told about statisticians. One member of the profession shows up at a bar and is persuaded, after several drinks, to join a game of darts. With money on the line, the statistician’s first toss lands a foot to the left of the target – and the second toss lands a foot to the right. With the gathered crowd still eager for the third toss, the statistician instead takes the mean of the two misses and pre-emptively declares “bulls-eye!”