# Poisson distribution Part 2

Does Poisson distribution arise from the binomial distribution? You can find out in Lesson 37.

Lesson 37 – Still counting – Poisson distribution

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# Poisson distribution

If we assume events are independent (the occurrence of one event does not affect the probability that a second event will occur), then the counts per unit interval can be assumed a random variable that follows a probability distribution. Counts, i.e., the number of times an event occurs in an interval follows a Poisson distribution.

Poisson distribution has one control parameter. It is the rate of occurrence; the average number of events per unit interval.

In lesson 36, we learn the fundamentals of Poisson distribution. You will also meet Able and Mumble two of my friends.

Lesson 36 – Counts: The language of Poisson distribution

# What is Return Period

Your recent vocabulary may include “100-year event” (happening more often), (drainage system designed for) “10-year storm,” and so on, courtesy mainstream media and news outlets.

Does a 10-year return period event occur diligently every ten years? Can a 100-year event occur three times in a row?

If we define T as a random variable that measures the time between the events (wait time or time to the next event or time to the first event since the previous event), the return period of the event is the expected value of T, i.e., E[T], its average measured over a large number of such occurrences.

In lesson 34, we learn about return period through Bob and his reappearance. Bob’s time of occurrence also relates to Geometric distribution.

Lesson 34 – I’ll be back: The language of Return Period

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