Excel GAMMADIST Function
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.
Note: The GAMMADIST function has been replaced with GAMMA.DIST. Although GAMMADIST is still available in current versions of Excel, you should consider using the new function from now on, because GAMMADIST may not be available in Excel’s future versions.
Syntax
=GAMMADIST(x, alpha, beta, cumulative)
Arguments
- x (required): The value at which you want to calculate the distribution. Note: x must be greater than or equal to 0.
- 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.
- cumulative (required): A logical argument that specifies the type of gamma distribution to be calculated:
- TRUE: Calculate the cumulative distribution function;
- FALSE: Calculate the probability density function.
Return Value
The GAMMADIST function returns a numeric value.
Function Notes
- GAMMADIST returns the #NUM! error if any of the below conditions is met:
- x < 0;
- alpha ≤ 0;
- beta ≤ 0.
- GAMMADIST returns the #VALUE! error if:
- x, alpha, or beta is not a numeric value;
- cumulative is not recognized as a logical value.
Example
To calculate both the cumulative distribution function and the probability density function for given x, alpha and beta values, you should set the cumulative argument as TRUE and FALSE respectively. Please copy or enter the formulas below in the result cells and then press Enter to get the results.
=GAMMADIST(B6,B9,B12,TRUE)
=GAMMADIST(B6,B9,B12,FALSE)
Also, you can type the actual x, alpha and beta values in the formulas as shown below.
=GAMMADIST(4,2,1.5,TRUE)
=GAMMADIST(4,2,1.5,FALSE)
GAMMADIST Vs. GAMMAINV
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 x, GAMMADIST(x, alpha, beta, TRUE) returns the value of probability such that x = GAMMAINV(probability, alpha, beta).
Related functions
The GAMMA.DIST 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.
The GAMMA function returns the value of the gamma function for a specified number.
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.
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