Top Qs
Timeline
Chat
Perspective
Poisson limit theorem
Probability Theory From Wikipedia, the free encyclopedia
Remove ads
In probability theory, the law of rare events or Poisson limit theorem states that the Poisson distribution may be used as an approximation to the binomial distribution, under certain conditions.[1] The theorem was named after Siméon Denis Poisson (1781–1840). A generalization of this theorem is Le Cam's theorem.

Remove ads
Theorem
Let be a sequence of real numbers in such that the sequence converges to a finite limit . Then:
First proof
Summarize
Perspective
Assume (the case is easier). Then
Since
this leaves
Remove ads
Alternative proof
Using Stirling's approximation, it can be written:
Letting and :
As , so:
Remove ads
Ordinary generating functions
It is also possible to demonstrate the theorem through the use of ordinary generating functions of the binomial distribution:
by virtue of the binomial theorem. Taking the limit while keeping the product constant, it can be seen:
which is the OGF for the Poisson distribution. (The second equality holds due to the definition of the exponential function.)
See also
References
Wikiwand - on
Seamless Wikipedia browsing. On steroids.
Remove ads