The Art of Statistics: Learning from Data

by David Spiegelhalter

George Gallup, who essentially invented the idea of the opinion poll in the 1930s, came up with a fine analogy for the value of random sampling. He said that if you have cooked a large pan of soup, you do not need to eat it all to find out if it needs more seasoning. You can just taste a spoonful, provided you have given it a good stir.

In a public attempt to make the process fair, 366 capsules were prepared, each containing a unique birthday, and capsules were intended to be picked from a box at random. But the capsules were put in the box in order of the month of the birthday, and were not properly mixed up. This might not have caused a problem if the men drawing out the capsules had delved down into the box, but as a remarkable video shows, they tended to take them from the top.4 The result was that it was bad luck to be born later in the year: 26 out of 31 birthdays in December ended up drafted, compared to only 14 in January.