Wednesday, April 18, 2018

It's Not The Data You Collect

It's not the data you collect, it's how you interpret that data that matters.

During WWII, when planes returned with battle damage they were repaired and returned to service. Because so many of the returning planes had damage in the wings and fuselage, there was a suggestion made to add armor to the areas that were showing damage.

That plan might have been carried out except for Abraham Wald. Dr. Wald was a statistician. He looked at the battle damage reports on returning aircraft and noticed the obvious. These were returning planes. That meant that the damage they had received was not enough to prevent them from flying.

Since he understood that aerial combat was never precise enough to hit another aircraft in an exact spot, but was simply shooting and getting hits wherever they might, he was only looking at part of the data. The rest of the data was smashed into the dirt of France and Germany. The planes that did not return held the real information.

Since those planes were unavailable for inspection, he reversed the thinking. Of the planes that had returned with battle damage, where had they not been hit? In the cockpit, engine, and tail. If additional armor plate was going to be effective, that's where it should be installed.

His logic carried the day, the Army Air Corps added armor as he suggested. If you can do graduate level statistics, here's the math behind it.


Borepatch said...

For folks who are interested (and mathematically inclined), the field of Operations Research is the formal name.

Old NFO said...

And that simple armor has graduated into the 'tubs' we see today in the likes of the A-10!

Will said...

Drawings like that, and the tv show "12 O'clock High" give the idea there is lots of room in the B-17. Not hardly! I'm a small guy, and moving around in that plane brings to mind an old-fashioned phone booth. Space is tight. Wearing the high-altitude cold-weather gear must have required the grace of a ballerina to move without hanging up on every protruding object and edge. That cockpit seems as tight as a Miata or RX-7.