May 9, 2021

How to use POISSON.DIST Function in Excel

Returns the Poisson distribution. A common application of the Poisson distribution is predicting the number of events over a specific time, such as the number of cars arriving at a toll plaza in 1 minute.

Syntax:= POISSON.DIST(x,mean,cumulative)

The POISSON.DIST function syntax has the following arguments:

• (required argument) – This is the number of events for which we want to calculate the probability. The value must be greater than or equal to 0.
• Mean (required argument) – This is the expected number of events. The argument must be greater than or equal to zero.
• Cumulative (required argument) – This is the logical argument that specifies the type of distribution to be calculated. It can either be:
• TRUE – Returns the cumulative Poisson probability that the number of random events occurring will be between zero and x inclusive.
• FALSE – Returns the Poisson probability mass function that the number of events occurring will be exactly x.

Example: Let’s look at some Excel POISSON.DIST function examples and explore how to use the POISSON.DIST function as a worksheet function in Microsoft Excel:

Suppose we are given the following data:

• Number of events: 20
• Expected mean: 25

To find out the Cumulative Poisson probability, we will use the following formula:

Syntax:  =POISSON.DIST(B1,B2,TRUE)

Result: 0.185492303

To find out the Poisson probability mass function, we will use the following formula:

Syntax: =POISSON.DIST(B1,B2,FALSE)

Result: 0.051917469

Note:

• If x is not an integer, it is truncated.
• If x or mean is nonnumeric, POISSON.DIST returns the #VALUE! error value.
• If x < 0, POISSON.DIST returns the #NUM! error value.
• If mean < 0, POISSON.DIST returns the #NUM! error value.
• POISSON.DIST is calculated as follows.

For cumulative = FALSE:

For cumulative = TRUE:

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