Protect the Areas that are not showing Hits.

WaldAbraham Wald was born  in 1902 in Transylvania which was part of Austria–Hungary and is now in Romania.  His family were devout Jews who would not allow the boy to attend school on Saturdays so he was home-schooled by his parents.

He was a brilliant mathematics student and he graduated  with a Ph D from the University of Vienna in 1931.  However, because of discrimination against Jews it was very difficult for him to gain employment.

When the Nazis invaded Austria in 1938, Wald managed to emigrate to the USA where he joined the Statistical Research Group (SRG) at Columbia University.  He was now able to bring his formidable skills in mathematics and operational research to military problems.

planeOne challenge involved examining the distribution of damage from German fire to aircraft – in particular bombers.  Extra protecting armour could be added to the plane but the more armour that was added the more weight that was carried.  Certain parts of the planes’ fuselage appeared to receive more hits from anti-aircraft fire.  The natural response from the military chiefs was to add more armour to these sections.   Wald challenged this notion.  He reasoned that enemy fire would be evenly distributed across the aircraft.  He also observed that the sample contained only those aircraft which had survived the mission and returned.  Consequently, the holes in the returning aircraft showed the areas where the plane could sustain damage and survive. Wald proposed that the Air Force reinforce the areas where the returning aircraft showed no damage as those were the areas where damage was lethal for the plane.  ‘Protect the areas that are not showing hits’.

His insights proved correct and the story is renowned as an example of counter-intuitive thinking and of the dangers of ‘survivorship bias’.’

After the war in 1950, Wald was invited to give a lecture tour in India.  Sadly, while there he and his wife were killed in a plane crash.

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