Survivorship Bias

focus on the winners

aka survival bias

definition survivorship bias is the logical error of concentrating on the people or things that made it past some selection process and overlooking those that did not --- https://en.wikipedia.org/wiki/Survivorship_bias

examples

• thinking that old buildings were sturdier and more beautiful, not realizing that weaker and uglier buildings have been torn down
• seeing a lot of successful restaurants in a city and concluding that the city is a good place to open a restaurant, not realizing that all the restaurants that went bankrupt aren't around for you to see

example the legend of Abraham Wald

The problem of armoring planes is assigned to Wald. Along with the assignment, he is given a fair amount of statistical data regarding aircraft damage, for example the location of damage from hits by enemy aircraft. It happens that most of the damage is located on the fuselage and very little in the area around motors, and the military is expecting to add armor to the fuselage, where the density of hits is highest. "Not so fast," said Wald. "What you should really do is add armor around the motors! What you are forgetting is that the aircraft that are most damaged don't return. You don't see them. Hits by German shells are presumably distributed somewhat randomly. The number of damaged motors you are seeing is far less than randomness would produce, and that indicates that it is the motors that are the weak point." The advice is taken, and in fact Wald's techniques for interpreting aircraft damage statistics continue through two later conflicts. --- Bill Casselman --- https://www.ams.org//publicoutreach/feature-column/fc-2016-06