Poisson distribution

(1.5 hours to learn)


The Poisson distribution is a discrete probability distribution for the counts of independent random events in a given time interval, e.g. babies born in a hospital in 1 month or lightening strikes in Mexico in 1 week. It is one of the most common discrete distributions used in virtually every scientific and financial field.


This concept has the prerequisites:

Core resources (read/watch one of the following)


Khan Academy: Probability and Statistics


Supplemental resources (the following are optional, but you may find them useful)


Mathematical Monk: Probability Primer (2011)
Online videos on probability theory.
Wolfram MathWorld

See also

  • Poisson processes are a kind of stochastic process where counts of events within a set follow a Poisson distribution.
  • For large values of the scale parameter, the Poisson distribution is well approximated by a Gaussian distribution. This follows from the Central Limit Theorem .
  • The Poisson distribution is a member of the exponential family .