GAMMAINV ( probability , alpha , beta )

Description: Computes the inverse of the gamma distribution. Given a value for probability, GAMMAINV seeks that value x such that GAMMADIST(x, alpha, beta, TRUE) = probability. Thus, the precision of GAMMAINV depends on the precision of GAMMADIST. GAMMAINV uses an iterative search technique.

Arguments:

Name	Type	Description
probability	number	The probability associated with the gamma distribution.
alpha	number	A parameter of the distribution.
beta	number	A parameter of the distribution. If beta = 1, GAMMAINV returns the standard gamma distribution.

Return Type and Value: number – The inverse of the gamma distribution.

However, if

• probability < 0 or probability > 1, #NUM! is returned.

• alpha ≤ 0 or beta ≤ 0, #NUM! is returned.

• The search has not converged after some implementation-defined number of iterations, #N/A is returned.

[Example:

GAMMAINV(0.068,9,2) results in 9.997130086

end example]