I’ve come to realize that I was wrong about a major aspect of probabilities.
They are inherently hard to grasp. That’s especially true for an individual event, like a war or election. People understand that if they roll a die 100 times, they will get some 1’s. But when they see a probability for one event, they tend to think: Is this going to happen or not?
They then effectively round to 0 or to 100 percent. That’s what the Israeli official did. It’s also what many Americans did when they heard Hillary Clinton had a 72 percent or 85 percent chance of winning. It’s what football fans did in the Super Bowl when the Atlanta Falcons had a 99 percent chance of victory.
And when the unlikely happens, people scream: The probabilities were wrong!
Usually, they were not wrong. The screamers were wrong.
It’s not enough to say an event has a 10 percent probability. People need a story that forces them to visualize the unlikely event — so they don’t round 10 to zero.
Imagine that a forecast giving Candidate X a 10 percent chance included a prominent link, “How X wins.” It would explain how the polling could be off and include a winning map for X. It would all but shout: This really may happen.
David Leonhardt, New York Times, December 24, 2017