Let the discrete random variable X denote the number of times an event occurs in an interval of time (or space). Then Xmay be a Poisson random variable with x = 0, 1, 2, ... Solution Let the discrete random variable X denote the number of times an event occurs in an interval of time (or space). Then Xmay be a Poisson random variable with x = 0, 1, 2, ....