(Moderator's note: thread moved from "Set Theory, Logic, Probability, Statistics") Hi guys, Say outside of my house, there are 20% chance of rain, and 40% chance the sprinker is on. When it is rain the pavement outside of house must be wet. And if the sprinkler is on, it also wet my pavement. If there is no rain and the sprinkler is off, my pavement is just dry. How do I calculate the probability of my pavement is dry? And I got the answer 52% from Netica. I think you all know netica is for bayesian network.