Despite overall similarities, all human beings are unique; they differ in intelligence, personality and special abilities, as well as in height, weight, beauty, and all sorts of other mental and physical variables. They also differ, as a consequence, in their ability to do satisfactory work in any of the many jobs, professions and callings which are provided in our society. Some are good at the job, some are not; taking quite simple occupations, it is usually found that the good do twice as much work as the bad. While a number of bottoms scoured by a good worker might amount to 500 or so a day, others only average 150 or thereabouts. In the weaving industry, when the total number of yards of cloth produced from the warp was measured for different workers, variations ranged from the rate of 62 picks per minute to 130 picks per minute. The same ratio has been found for hourly piece-work earnings of hosiery workers, pounds of women’s hose produced per hour by knitting-machine operators, and earnings of taxicab drivers working under similar conditions. As the work becomes more complex and demanding, the ratio becomes even greater, so that a good physicist produces work many times better than the bad physicist, and the outstanding entrepreneur exceeds many times the success rate of those less talented.
As a consequence, people have always tried to select those likely to succeed, and to reject those likely to fail, using many different types of method to establish such a likelihood. Perhaps one of the oldest examples is to be found in the Bible, where Gideon is reported to have used a two-stage selection procedure in his war against the Midianites.
Even earlier than Gideon, the ancient Chinese used selection tests, not very dissimilar to our own, in the selection of clerics and other civil servants, as we now call them. The method worked well in producing highly intelligent, diligent and literate people to run the civil service, and the stability of the Chinese Empire owed much to the people so selected.
Nowadays, business and government use many different selection devices, some good, some bad and some indifferent. For the selection of high-level