A Poisson random variable X with parameter λ > 0 has distribution Find the expectation and variance of X. (Poisson random variables are used for modeling the random flow of events such as motorists...

A Poisson random variable X with parameter λ > 0 has distribution

Find the expectation and variance of X. (Poisson random variables are used for modeling the random flow of events such as motorists arriving at a toll booth or calls arriving at a service center.)