Excel GAMMAINV Function
The GAMMAINV function returns the inverse of the gamma cumulative distribution. The function is frequently used to provide probabilities for values that may have a skewed distribution, such as queuing analysis.
Note: The GAMMAINV function has been replaced with GAMMA.INV. Although GAMMAINV is still available in current versions of Excel, you should consider using the new function from now on, because GAMMAINV may not be available in Excel’s future versions.
Syntax
=GAMMAINV(probability, alpha, beta)
Arguments
- probability (required): The probability for which to evaluate the inverse gamma cumulative distribution. Note: probability must satisfy the equation: 0 ≤ probability < 1.
- alpha (required): A parameter of the distribution. Note: alpha must be positive.
- beta (required): A parameter of the distribution. If beta = 1, then the standard gamma distribution is calculated. Note: beta must be positive.
Return Value
The GAMMAINV function returns a numeric value.
Function Notes
- GAMMAINV returns the #NUM! error if any of the below conditions is met:
- probability < 0 or probability ≥ 1;
- alpha ≤ 0;
- beta ≤ 0.
- GAMMAINV returns the #VALUE! error if probability, alpha, or beta is not a numeric value.
Example
To calculate the value of the inverse gamma cumulative distribution for the given probability, alpha and beta values, please copy or enter the formula below in the result cell and then press Enter to get the result.
=GAMMAINV(B6,B9,B12)
Also, you can type the actual probability, alpha and beta values in the formula as shown below.
=GAMMAINV(4,2,1.5)
GAMMAINV Vs. GAMMADIST
The Excel GAMMAINV function is the inverse of the GAMMADIST function (when used to calculate the cumulative distribution function, i.e., the cumulative argument is set to TURE). For a supplied value for probability, GAMMAINV(probability, alpha, beta, TRUE) returns the value of x such that probability = GAMMADIST(x, alpha, beta, TRUE).
Related functions
The GAMMA.INV function returns the inverse of the gamma cumulative distribution. The function is frequently used to provide probabilities for values that may have a skewed distribution, such as queuing analysis.
The GAMMA function returns the value of the gamma function for a specified number.
The GAMMADIST function returns the gamma distribution. The function is frequently used to provide probabilities for values that may have a skewed distribution, such as queuing analysis.
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