The Random Variables add-in allows a completely general
discrete distribution where the random variables are allowed
to assume a finite set of arbitrary values. We describe the
set of random variable values as X. A number
is associated with each value of the set that is the probability
of that random variable value. The add-in does not require
these values to sum to 1, but a valid distribution is obtained
by dividing each value by the sum.
The values in the set X need not be integer.