Updated: 9 August 2010
Use POISSON to calculate the Poisson distribution. The formula for the probability density function (pdf) is:
The formula for the cumulative distribution function (cdf) is:
Where Q(a,x) is the regularized gamma function
Syntax
SELECT [wctStatistics].[wct].[POISSON] (
<@X, float,>
,<@Mean, float,>
,<@Cumulative, bit,>)
Arguments
@X
is the number of events. @X is an expression of type float or of a type that can be implicitly converted to float.
@Mean
is the arithmetic mean of the distribution. @Mean is an expression of type float or of a type that can be implicitly converted to float.
@Cumulative
is a logical value that determines if the probability density function (False, 0) or the cumulative distribution function (True, 1) is being calculated.
Return Types
float
Remarks
· @X is truncated to zero decimal places.
· If @X < 0, POISSON returns an error.
· If @Mean < 0, POISSON returns an error.
Examples
select wct.POISSON(2,5,'False')
This produces the following result
----------------------
0.0842243374885683
(1 row(s) affected)
select wct.POISSON(2,5,'True')
This produces the following result
----------------------
0.124652019483081
(1 row(s) affected)
Select wct.GAMMAQ(3, 5)
This produces the following result
----------------------
0.124652019483081
(1 row(s) affected)