I herd this in context of asking good questions for Data Science.
How A Story From World War II Shapes Facebook Today | Co.Design | business + design
"In WWII, Allied bombers were key to strategic attacks, yet these lumbering giants were constantly shot down over enemy territory. The planes needed more armor, but armor is heavy. So extra plating could only go where the planes were being shot the most.
...Wald flipped conventional logic on its head. He said the military didn’t need to reinforce the spots that had bullet holes. They needed to reinforce the spots that didn’t have bullet holes.
Because the planes that had been shot in these bullet-free zones never made it home to be accounted for."
Data Science and R - Philly.NET (Malvern, PA) | Meetup