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WorksheetFunction.GammaInv Method (Excel)

Returns the inverse of the gamma cumulative distribution. If p = GAMMADIST(x,...), then GAMMAINV(p,...) = x.

Important note Important

This function has been replaced with one or more new functions that may provide improved accuracy and whose names better reflect their usage. This function is still available for compatibility with earlier versions of Excel. However, if backward compatibility is not required, you should consider using the new functions from now on, because they more accurately describe their functionality.

For more information about the new function, see the Gamma_Inv method.

expression .GammaInv(Arg1, Arg2, Arg3)

expression A variable that represents a WorksheetFunction object.

Parameters

Name

Required/Optional

Data Type

Description

Arg1

Required

Double

Probability - the probability associated with the gamma distribution.

Arg2

Required

Double

Alpha - a parameter to the distribution.

Arg3

Required

Double

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

Return Value

Double

You can use this function to study a variable whose distribution may be skewed.

  • 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 64 iterations, the function returns the #N/A error value.

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