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POISSON

Syntax:

POISSON ( x , mean , cumulative-flag )

Description: Computes the Poisson distribution.

Mathematical Formula:

For cumulative-flag = FALSE:

For cumulative-flag = TRUE:

Arguments:

Name

Type

Description

x

number

The number of events, truncated to an integer.

mean

number

The expected numeric value.

cumulative-flag

logical

Determines the form of the function. If TRUE, POISSON returns the cumulative Poisson probability that the number of random events occurring will be between zero and x, inclusive; if FALSE, it returns the Poisson probability mass function that the number of events occurring will be exactly x.

 

Return Type and Value: number – The Poisson distribution.

However, if

x < 0, #NUM! is returned.

mean ≤ 0, #NUM! is returned.

[Example:

POISSON(2,5,TRUE) results in 0.124652019
POISSON(2,5,FALSE) results in 0.084224337

end example]