WorksheetFunction.Gamma_Dist 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.
Version Information
Version Added: Excel 2010
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:
.gif "Ff839080.awfgmdi1_ZA06051146(en-us,office.14).gif")
The standard gamma probability density function is: .gif "Ff839080.awfgmdi2_ZA06051147(en-us,office.14).gif")
When alpha = 1, GAMMA_DIST returns the exponential distribution with:
.gif "Ff839080.awfgmdi3_ZA06051148(en-us,office.14).gif")
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.