The poisson random variable

The poisson random variable

The probability mass function for a Poisson random variable is: $$ f_X(x) = P(X=x) = \frac{\lambda^x}{x!} e^{-\lambda} $$ where $\lambda$ is a parameter. The expectation and variance of this random variable are $\mathbb{E}(X) = \lambda$ and $\textrm{var}(X) = \lambda$.

Syllabus Aims

  • You should be able to explain how the Poisson distribution can be derived from the binomial distribution in the limit as $n \rightarrow \infty$
  • You should be able to write out the probability mass function for the Poisson random variable.
  • You should be able to show that the Poisson random variable is properly normalised.
  • You should be able to derive the moment generating functions for the poisson random variable and hence obtain the expectation and variance for this random variable

Description and link

Module

Author

Problems involving the Poisson Random variable. SOR3012 G. Tribello

Contact Details

School of Mathematics and Physics,
Queen's University Belfast,
Belfast,
BT7 1NN

Email: g.tribello@qub.ac.uk
Website: mywebsite