ABSTRACT
It is apparent from the table above that the notation p(x,y) for the joint pmf of the variables X and Y will be ambiguous in many situations; without indicating which variable is which, p(a,b) might represent either P(X = a,Y = b) or P(Y = a,X = b). A more cumbersome, but unambiguous, notation for bivariate probabilities is the following. Let
pX ,Y (x,y) = P(X = x,Y = y).
