WorksheetFunction.Gamma_Dist method (Excel)
Returns the gamma distribution. Use this function to study variables that may have a skewed distribution. The gamma distribution is commonly used in queuing analysis.
Syntax
expression.Gamma_Dist (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, Gamma_Dist returns the standard gamma distribution. |
| Arg4 | Required | Boolean | Cumulative - a logical value that determines the form of the function. If cumulative is True, Gamma_Dist returns the cumulative distribution function; if False, it returns the probability density function. |
Return value
Double
Remarks
If x, alpha, or beta is nonnumeric, Gamma_Dist returns the #VALUE! error value.
If x < 0, Gamma_Dist returns the #NUM! error value.
If alpha ≤ 0 or if beta ≤ 0, Gamma_Dist returns the #NUM! error value.
The equation for the gamma probability density function is:
The standard gamma probability density function is:
When alpha = 1, Gamma_Dist returns the exponential distribution with:
For a positive integer n, when alpha = n/2, beta = 2, and cumulative = True, Gamma_Dist returns (1 - CHIDIST(x)) with n degrees of freedom.
When alpha is a positive integer, Gamma_Dist is also known as the Erlang distribution.
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