Joint and Conditional Distributions
More than one random variable can be defined over a sample space. In this case, we talk about a joint or multivariate probability distribution.
The joint probability mass function for two discrete random variables X and Y is: p(x,y)=P(X=x, Y=y)
The marginal probability mass function totals up the probability masses for the values of each variable separately.
Similar intersection rules hold for joint distributions as for events.