Lasse Lien:

“During World War 2 the British Royal Air Force (and Navy) pioneered the use of empirical and statistical analysis to improve performance.  The RAF collected large amounts of data on exactly where returning aircraft had received damage [from German air-defence fire]. The intuitive recommendation would be to reinforce the aircrafts were the data indicated they took the most damage.  However, realizing that they only had data from surviving aircraft, the [Operations Research] group under leadership of Patrick Blackett recommended that they reinforce the aircraft in the sections where no damage was recorded in the data.”