>Please, what number of cats did not leave the ship before a fatal voyage? That actually doesn't matter too much. As long as the cats which do leave the ship i

>Please, what number of cats did not leave the ship before a fatal voyage? That actually doesn't matter too much. As long as the cats which do leave the ship is a predictor of disaster. Even a slight correlation, say 1%, would be useful; do you want to take a 1% risk to your life? Maybe buy an extra lifeboat or something? Of course, the prior probability of this hypothesis is pretty low, but it isn't to superstitious people.