Definition. Finite probability law [ftip-000B]
Definition. Finite probability law [ftip-000B]
Using the notation of Notation [ftip-000A], a finite probability law on \(X\) is an element \(p\in \Delta (X)\). For an event \(A\subseteq X\), its probability is \[ p(A)=\sum _{x\in A}p(x). \] For \(p(A)>0\), the conditional law on \(B\subseteq X\) is \(p(B\mid A)=p(A\cap B)/p(A)\).