use it to simplify our math here's a simple example so we have a robot trying to see if the doors open or not okay what's the probability of doors open given some measurement of the sensor of the robot it is to illustrate that kind of reasoning behind why we often use Bayes rule probability of being open given some measurement is a diagnostic distribution it's kind we're trying to diagnose what's the state given a measurement but those distributions often we cannot build we cannot deliver a sensor with that distribution because I mean you can't do