A-Level Further Maths · Further Statistics
Poisson Distribution
What is it
The Poisson distribution models the number of times a random event occurs in a fixed interval of time or space, given a known average rate — such as the number of customers arriving at a shop per hour.
Why it matters
The Poisson distribution is used throughout real-world modelling of rare, independent events — call centre traffic, radioactive decay, network failures — anywhere events happen at a known average rate but at random individual moments.
Exam tip
Before applying the Poisson distribution, check that the mean and variance of the given data are approximately equal — this is a defining property of the Poisson distribution, and a significant mismatch is a clue that a different distribution is more appropriate.
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