that the rain will cause x and y independently it's not related directly whether pavement is wet and somebody cares umbrella it's through the fact that it rains which is the common cause for both of them and said I'll make x and y independent given see another example and the one that we'll see most often in this class is if you know the state of the world then every sensor for every sense you're reading might be independent very often because if your sensor just acts on the real state of the world then the reading that happens