Can someone explain the phase scape in Monte Carlo simulation. what does it mean "the probabiliy density pre-factor disappear" in that context.

Need to calculate (A) = f p(I')A(I')dI' in multi-dimensional phase space It If we have a scheme to sample I]- in accordance to p(I'), then this can be approximated as 1 (A) = In p(f')A(F)dF :3 E: Am) Note: the probability density' pre-factor disappears, since I";- have the corresponding density A particular combination of coordinates and velocities of each particle defines a state of the system: a point F in the (SN-dimensional phase space