### POISSON(x, mean, cumulative)

Returns the probability of getting less than or equal to a particular value in a poisson distribution.

 x The number of events. mean The expected numeric value. cumulative The type of function to useTrue = cumulative probability functionFalse = probability mass function

#### Remarks

 * POISSON.DIST was added in Excel 2010 to replace this function.* The Poisson distribution is a discrete 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.* If "x" is not an integer, it is truncated.* If "x" is not numeric, then #VALUE! is returned.* If "mean" is not numeric, then #VALUE! is returned.* If "mean" = 0, then #NUM! is returned.* If "x" < 0, then #NUM! is returned.* If "x" = 0, then* In Excel 2010 the accuracy of this function was improved.* For the Microsoft documentation refer to support.office.com

 A 1 =POISSON(2,5,FALSE) = 0.084 2 =POISSON(2,5,TRUE) = 0.125 3 =POISSON(2,2,1) = 0.677 4 =POISSON(-2,2,1) = #NUM!