The W. Edwards Deming Institute Blog

Is the Result Due to Mathematical Probability or Individual Merit?

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Dr. Deming was constantly learning from others. He also pointed out that we can be led astray by failing to understand data. This quote, included in Out of the Crisis (page 394), shows both of those traits and illustrates a common trap of performance appraisal – using evidence that is highly questionable to claim individual merit is responsible when it well could just be mathematical probability.

The quote is from The Face of Battle by John Keegan:

As to the influence and genius of great generals — there is a story that Enrico Fermi once asked Gen. Leslie Groves how many generals might be called “great.” Groves said about three out of every 100. Fermi asked how a general qualified for the adjective, and Groves replied that any general who had won five major battles in a row might safely be called great. This was in the middle of World War II. Well, then, said Fermi, considering that the opposing forces in most theaters of operation are roughly equal, the odds are one of two that a general will win a battle, one of four that he will win two battles in a row, one of eight for three, one of sixteen for four, one of thirty-two for five. “So you are right, general, about three out of every 100. Mathematical probability, not genius.”

Understanding data is important in order to practice evidence based management. Every system has variation when you reward, or blame, people based on how the variation falls when they are around that is likely not a particularly helpful practice.

Related: The Annual Appraisal: Destroyer of People
Illusions – Optical and Incorrect Conclusions – Dr. Deming: “The TUC meeting in London, entertained a motion, made and seconded, that no wage paid in this country shall be bellow average. It failed by 3 votes. How I wish it had passed. Wouldn’t that be funny.”


Categorised as: understanding variation


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