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.

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 GAMMA.INV function.

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.

Example

The example may be easier to understand if you copy it to a blank worksheet.

How do I copy an example?

  1. Select the example in this article.

    Important   Do not select the row or column headers.

    selecting an example from help

    Selecting an example from Help

  2. Press CTRL+C.

  3. In Excel, create a blank workbook or worksheet.

  4. In the worksheet, select cell A1, and press CTRL+V.

    Important   For the example to work properly, you must paste it into cell A1 of the worksheet.

  5. To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.

After you copy the example to a blank worksheet, you can adapt it to suit your needs.

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Data

Description

0.068094

Probability associated with the gamma distribution

9

Alpha parameter to the distribution

2

Beta parameter to the distribution

Formula

Description (Result)

=GAMMAINV(A2,A3,A4)

Inverse of the gamma cumulative distribution for the above terms (10.00001131)

Applies To: Excel 2010, Excel Starter, Excel Online, SharePoint Online



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