# WorksheetFunction.Poisson_Dist (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 one minute.

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:

Poisson_Dist (Arg1, Arg2, Arg3)

``````
Dim dblArg1 As Double: dblArg1 =
Dim dblArg2 As Double: dblArg2 =
Dim dblPoisson_Dist As Double
dblPoisson_Dist = WorksheetFunction.Poisson_Dist(Arg1:=dblArg1, Arg2:=dblArg2, Arg3:=True)
``````

## Arguments

Arg1, Arg2, Arg3

Arg1 (Double) - X - The number of events.

Arg2 (Double) - Mean - The expected numeric value.

Arg3 (Boolean) - Cumulative - A logical value that determines the form of the probability distribution returned. If cumulative is True, Poisson_Dist returns the cumulative Poisson probability that the number of random events occurring will be between 0 (zero) and x inclusive; if False, it returns the Poisson probability mass function that the number of events occurring will be exactly x.