Question

What are the four rules that have to be followed to use a Poisson distribution?

Answer 1

What are the four rules that have to be followed to use a Poisson distribution?

In probability theory, the Poisson distribution is about probability distribution. A Poisson distribution helps in describing the probability of occurrence of a number of events in certain given time interval.

The four basic rules are

1. Random – This means an even can occur any number of times during a period.
2. Average rate of occurrence is constant – this means the rate does not change with time
3. Independent – This means if an even occurs it does not affect the probability of another event occurring in the same period
4. Probability of an event occurring is proportional to the length of the time period

Example :

Let us check how Poissons distribution is appropriate for number of phone calls an office receives at noon.

Average is 10 calls per hours during noon.

1. Although total number of calls are 10, they can take any number of calls during the period
2. Occurrence rate is assumed to be constant
3. As the events are independent, hence no caller is affecting the chances of another person calling
4. Probability of getting a call in first half hour is the same as the probability of getting the call in the second half hour.