Hello, Sharov, you wrote: S> Hello, paul.marx, you wrote: PM>> I Welcome! PM>> torments a question: why in bayesian probability probability of joint approach often events express through 1 minus product of reverse probabilities? What sense in it? PM>> for example, PM>> P (y=1|x1, x2) = 1 - (1 - p1) * (1 - p2) PM>> where PM>> P (y=1|x1, x2) - probability of approach of event y=1, depending on presence of factors x1 and x2, PM>> pi - the probability of appearance of the factor xi S> Can simply intuitively easier and more clear by contradiction yes is not present, there any deep thought behind this all is covered. Only it disappears from me. But here already on a statement in a type from reverse, removing the brackets we receive P (y=1|x1, x2) = p1 + p2 + p1*p2 instead of as in forehead P (y=1|x1, x2) = p1*p2 so behind all it something should be...