WorksheetFunction.GammaDist Method
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.
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:
The standard gamma probability density function is:
- When alpha = 1, GAMMADIST returns the exponential distribution with:
- 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.