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Posts Tagged ‘Deming

“Gentlemen, you need to add armor-plate where the holes aren’t, because that’s where the holes were on the airplanes that didn’t return”*…

Diagram of bullet-holes in WWII bombers that returned

Allied bombers were key to Britain’s air offensive against Germany during the second world war. As such, the RAF wanted to armour their bombers to prevent them from being shot down. But armour is heavy – you cannot reinforce an entire bomber and still have it fly. So statistician Abraham Wald was asked to advise on where armour should be placed on a bomber.

After each wave of bombing, every returning aircraft was meticulously examined and a note was made of where each aircraft had sustained damage by the Germans. The image [above] conceptualises what Wald’s data might have looked like visually.

So what was Wald’s advice? Where should armour be added?

He essentially advised the RAF to add armour to places where you do not find bullet holes. Wait… what?!

Wald wisely understood that the data was based only on planes that survived. The planes that did not survive were likely to have sustained damage on the areas where we do not observe bullet holes – such as around the engine or cockpit…

Making better decisions: one of the most prevalent– and insidious– forms of selection bias, survivorship bias, illustrated: “How to armour a WWII bomber.”

See also: “How to avoid being duped by survivorship bias.”

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As we think clearly, we might send productive birthday greetings to W. Edwards Deming; he was born on this date in 1900. An engineer, statistician, professor, author, lecturer, and management consultant, he helped develop the sampling techniques still used by the U.S. Department of the Census and the Bureau of Labor Statistics.

But he is better remembered as the champion of statistically-based production management techniques that first gained traction in post-WWII Japan, where many credit Deming as a key ingredient in what has become known as the Japanese post-war economic miracle of 1950 to 1960, when Japan rose from the ashes of war onto the its path to becoming the second-largest economy in the world– through processes shaped by the ideas Deming taught. In 1951, the Japanese government established the Deming Prize in his honor.

While his impact in Japan (finally) brought him to the attention of business leaders in the U.S., he was only just beginning to win widespread recognition in the U.S. at the time of his death in 1993.

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