# GAMMAINV function

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.

## Syntax

GAMMAINV(probability,alpha,beta)

Probability     is the probability associated with the gamma distribution.

Alpha     is a parameter to the distribution.

Beta     is a parameter to the distribution. If beta = 1, GAMMAINV returns the standard gamma distribution.

## Remarks

• If any argument is nonnumeric, 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.

GAMMAINV uses an iterative technique for calculating the function. Given a probability value, GAMMAINV iterates until the result is accurate to within ±3x10^-7. If GAMMAINV does not converge after 100 iterations, the function returns the #N/A error value.

## Example

Probability

Alpha

Beta

Formula

Description (Result)

0.068094

9

2

=GAMMAINV([Probability],[Alpha],[Beta])

Inverse of the gamma cumulative distribution for the arguments (10)

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