GAMMADIST

GAMMADIST(x, alpha, beta, cumulative)

Returns the probability distribution function OR the cumulative probability function for a gamma distribution.

x	The number from the distribution.
alpha	The first parameter to the distribution.
beta	The second parameter to the distribution.
cumulative	A logical value indicating the type of function to use: False (or 0) = individual probability (equal to) True (<> 0) = cumulative probability (equal to or less than)

REMARKS

* GAMMA.DIST was added in Excel 2010 to replace this function.
* This function is only available for backwards compatibility and should not be used.
* The gamma distribution is a continuous distribution
* If "x" < 0, then #NUM! is returned.
* If "x" is not numeric, then #VALUE! is returned.
* If "alpha" = 0, then #NUM! is returned.
* If "alpha" is not numeric, then #VALUE! is returned.
* If "beta" = 1, then the standard gamma distribution is used.
* If "beta" = 0, then #NUM! is returned.
* If "beta" is not numeric, then #VALUE! is returned.
* The "cumulative" argument is not optional.
* If "cumulative" = False, then the height of the curve at "x" is returned.
* If "cumulative" = True, then the area under the curve to the left of "x" is returned.
* This function is also known as the Erlang distribution, when "alpha" is a positive integer.
* You can use the GAMMA.INV function to return the inverse of the cumulative probability function for a gamma distribution.
* You can use the GAMMA function to return the gamma function value.
* You can use the BETA.INV function to return the inverse of the cumulative probability function for a beta distribution.
* For the Microsoft documentation refer to support.microsoft.com

	A
1	=GAMMADIST(10, 9, 2, FALSE) = 0.033
2	=GAMMADIST(10, 9, 2, TRUE) = 0.068
3	=GAMMADIST(10, 10, 5, TRUE) = 0
4	=GAMMADIST(7, 5, 1, TRUE) = 1
5	=GAMMADIST(GAMMAINV(0.5, 4, 2), 4, 2, TRUE) = 1
6	=GAMMADIST(10, 9, 0, TRUE) = #NUM!
7	=GAMMADIST(10, -2, 2, TRUE) = #NUM!
8	=GAMMADIST(-1, 9, 2, TRUE) = #NUM!
9	=GAMMADIST(-1, "some text", 2, TRUE) = #VALUE!
10	=GAMMADIST(-1, 9, 2, "some text") = #VALUE!