Poisson Distribution – Proof

Property 1: Suppose the probability p of success of a single trial approaches 0 while the number of trials n approaches infinity and the value μ = np stays fixed. Then the binomial distribution B(n, p) approaches the Poisson distribution with mean μ.

Proof: Let f(x) be the pdf for a binomial distribution as described in the statement of the theorem. Then

image3292

image3293

image3294

Now
image3295

where z = -p. But
image3297

and so
image3298

Also
image3299

Thus as p → 0 and n\infty, with μ = np fixed, we have

image3301

which completes the proof.

References

Hoel, P. (1962) Introduction to mathematical statistics, 3rd Ed. John Wiley and Sons

Chamberlain, A. (2016) Deriving the Poisson distribution from the binomial distribution
https://medium.com/@andrew.chamberlain/deriving-the-poisson-distribution-from-the-binomial-distribution-840cc1668239

ProofWiki (2021) Binomial distribution approximated by Poisson distribution
https://proofwiki.org/wiki/Binomial_Distribution_Approximated_by_Poisson_Distribution#:~:text=Binomial%20Distribution%20Approximated%20by%20Poisson%20Distribution,-From%20ProofWiki&text=Let%20X%20be%20a%20discrete,%CE%BBkk!e%E2%88%92%CE%BB

4 thoughts on “Poisson Distribution – Proof”

  1. Dear George.
    I have built a poissons distribution model in excel to try n guide me on my betting on soccer matches.Am not yet very good at it.Pse try n use the data below for a match and cal the propable outcome of the game:

    Home Draw Away Home or Draw Double chance Away or Draw Under 2.5 over 2.5 BTTS BTTN ODD EVEN
    1.23 5.83 16 1.04 1.11 1.9 1.9 1.9 2.76 1.34 1.92 1.76
    NB: ODD/EVEN: are prob that the out come of the game after the 90 mins will be an even or odd number.I would love to follow your method if the results are close to the outcome.
    Regards.

    Reply
    • Kenneth,
      Sorry, but I don’t understand the data nor the goal. When you say that the outcome is odd or even, are you referring to the total points scored by both sides?
      Charles

      Reply
    • George,
      Sorry, but I can’t make the lecture notes available via email. I plan to provide a book which contains these lecture notes which you can purchase for a modest fee, but the book is not yet available.
      Charles

      Reply

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