GAMMAINV

Definition

Returns the inverse of the gamma cumulative distribution. If p = GAMMADIST(x,...), then GAMMAINV(p,...) = x. You can use this function to study a variable whose distribution may be skewed.

Sample Usage

Syntax

GAMMAINV(probability,alpha,beta)

The GAMMAINV function syntax has the following arguments:

• Probability     Required. The probability associated with the gamma distribution.

• Alpha     Required. A parameter to the distribution.

• Beta     Required. A parameter to the distribution. If beta = 1, GAMMAINV returns the standard gamma distribution.

Remarks

• If any argument is text, GAMMAINV returns the #VALUE! error value.

• If probability < 0 or probability > 1, GAMMAINV returns the #NUM! error value.

• If alpha ≤ 0 or if beta ≤ 0, GAMMAINV returns the #NUM! error value.

Given a value for probability, GAMMAINV seeks that value x such that GAMMADIST(x, alpha, beta, TRUE) = probability. Thus, precision of GAMMAINV depends on precision of GAMMADIST. GAMMAINV uses an iterative search technique. If the search has not converged after 100 iterations, the function returns the #N/A error value.