Tag: World War II

Statistics in a time of war

John D. Cook shares this interesting piece of history:

During WWII, statistician Abraham Wald was asked to help the British decide where to add armor to their bombers. After analyzing the records, he recommended adding more armor to the places where there was no damage!

This seems backward at first, but Wald realized his data came from bombers that survived. That is, the British were only able to analyze the bombers that returned to England; those that were shot down over enemy territory were not part of their sample. These bombers’ wounds showed where they could afford to be hit. Said another way, the undamaged areas on the survivors showed where the lost planes must have been hit because the planes hit in those areas did not return from their missions.

Wald assumed that the bullets were fired randomly, that no one could accurately aim for a particular part of the bomber. Instead they aimed in the general direction of the plane and sometimes got lucky.

It stories like this one, of a practical application, that make me regret of being a bad student.  I think that more of these should be a part of a curriculum.

Bayes theorem history

A fascinating read on the Bayes theorem history:

The German codes, produced by Enigma machines with customizable wheel positions that allowed the codes to be changed rapidly, were considered unbreakable, so nobody was working on them. This attracted Alan Turing to the problem, because he liked solitude. He built a machine that could test different code possibilities, but it was slow. The machine might need four days to test all 336 wheel positions on a particular Enigma code. Until more machines could be built, Turing had to find a way for reducing the burden on the machine.

He used a Bayesian system to guess the letters in an Enigma message, and add more clues as they arrived with new data. With this method he could reduce the number of wheel settings to be tested by his machine from 336 to as few as 18. But soon, Turing realized that he couldn’t compare the probabilities of his hunches without a standard unit of measurement. So, he invented the ‘ban’, defined as “about the smallest change in weight of evidence that is directly perceptible to human intuition.” This unit turned out to be very similar to the bit, the measure of information discovered using Bayes’ Theorem while working for Bell Telephone.

If the whole thing is too much for you, at least read the “Bayes at War” section.

Victory Day photography

I’m catching up with some of my RSS subscriptions, so this is a few days late.  On May 9th, Russia and other ex-USSR countries celebrate the Victory Day over the Nazi Germany in the World War II.  Big Picture has an excellent collection of photos covering the celebrations.

Pages of history

Yesterday I came across this collection of nostalgic photographs that bring back memories from the USSR times.   I was too young to see some of those images in real life, but they still have meaning to me.  Most though are as they were back then.

Yet, these are staged photographs of some every day items.   Today I came across something much more real and something much more dramatic.  It is again a collection of images, but in a video form.  The video shows the staggering difference between the modern day Saint Petersburg and Leningrad (as it was called back then) during the Siege.  As Wikipedia puts it: “It was one of the longest and most destructive sieges in history and one of the most costly in terms of human casualties”.  It lasted for 872 days and it took lives of millions of people.  As per Wikipedia: 1,017,881 were killed, captured, or missing and 2,418,18 wounded or sick from the Red Army forces.  Civilian casualties are in the numbers of 642,000 during the siege and 400,000 at evacuations.  These are only those numbers that were verified.  In reality that was much more.

[youtube=http://www.youtube.com/watch?v=SQ9LGdamU20]

Sergey Larenkov : Now and Then

Sergey Larenkov seems to be spending quite a lot of time producing stunning images which combine photographs of the same place as it is now and as it used to be during the World War II.

If I saw something like this back when I was struggling through boredom of my history lessons, I think I would have done much better.  This stuff is awesome!