Probability Mass Function

A Probability Mass Function is a Probability Function for a Discrete Distribution, that is, where the Random Variable is Discrete. It is called a mass function, because each probability value per discrete Outcome is like a point mass.

• $|S|\le {\aleph }_0$
• $\forall x\in S,f(x)=P(X=x)$
• $\forall x\in S,f(x)\ge 0$
• ${\sum }_{-\infty }^{\infty }f(x)=1$