Let X be a discrete random variable where probability of X = x is given by
the probability distribution of X is said to be Poisson distribution with parameter m. Here m is mean of the distribution. Poisson distribution is a limiting form of binomial distribution where p is very small and n is large enough such that np = m (Constant).
Mean, Variance and Standard Deviation of Poisson Distribution:
Second Moment about origin:
Second Moment about mean: