WorksheetFunction.GammaDist Method (Excel)
Returns the gamma distribution. You can use this function to study variables that may have a skewed distribution. The gamma distribution is commonly used in queuing analysis.
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_Dist method.
Syntax
expression .GammaDist(Arg1, Arg2, Arg3, Arg4)
expression A variable that represents a WorksheetFunction object.
Parameters
Name |
Required/Optional |
Data Type |
Description |
|---|---|---|---|
Arg1 |
Required |
Double |
X - the value at which you want to evaluate the distribution. |
Arg2 |
Required |
Double |
Alpha - a parameter to the distribution. |
Arg3 |
Required |
Double |
Beta - a parameter to the distribution. If beta = 1, GAMMADIST returns the standard gamma distribution. |
Arg4 |
Required |
Boolean |
Cumulative - a logical value that determines the form of the function. If cumulative is TRUE, GAMMADIST returns the cumulative distribution function; if FALSE, it returns the probability density function. |
Return Value
Double
Remarks
If x, alpha, or beta is nonnumeric, GAMMADIST returns the #VALUE! error value.
If x < 0, GAMMADIST returns the #NUM! error value.
If alpha ≤ 0 or if beta ≤ 0, GAMMADIST returns the #NUM! error value.
The equation for the gamma probability density function is:
.gif "Ff841156.awfgmdi1_ZA06051146(en-us,office.14).gif")
The standard gamma probability density function is: .gif "Ff841156.awfgmdi2_ZA06051147(en-us,office.14).gif")
When alpha = 1, GAMMADIST returns the exponential distribution with:
.gif "Ff841156.awfgmdi3_ZA06051148(en-us,office.14).gif")
For a positive integer n, when alpha = n/2, beta = 2, and cumulative = TRUE, GAMMADIST returns (1 - CHIDIST(x)) with n degrees of freedom.
When alpha is a positive integer, GAMMADIST is also known as the Erlang distribution.