 In a discrete probability distribution of a random variable "X", the mean is equal to the sum over every possible value weighted by the probability of that value; that is, it is computed by taking the product of each possible value "x" of "X" and its probability "p"("x"), and then adding all these products together, giving formula_5.An analogous formula applies to the case of a continuous probability distribution.Not every probability distribution has a defined mean; see the Cauchy distribution for an example.