 where \(\int_X\) is the integral over the phase space  \(X\).[6]  If the space consists of discrete elements, like the students of the school (they are ‘discrete’ in that you can count them), then the integral becomes equivalent to a sum like the one we have when we determine the average height of a population. If the \(X\) is continuous (as the phase space above) things are a bit more involved.