WorksheetFunction.GammaDist(Double, Double, Double, Boolean) Method
Definition
Important
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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.
public:
double GammaDist(double Arg1, double Arg2, double Arg3, bool Arg4);public double GammaDist (double Arg1, double Arg2, double Arg3, bool Arg4);Public Function GammaDist (Arg1 As Double, Arg2 As Double, Arg3 As Double, Arg4 As Boolean) As DoubleParameters
- Arg1
- Double
X - the value at which you want to evaluate the distribution.
- Arg2
- Double
Alpha - a parameter to the distribution.
- Arg3
- Double
Beta - a parameter to the distribution. If beta = 1, GammaDist returns the standard gamma distribution.
- Arg4
- 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.
Returns
Remarks
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(Double, Double, Double, Boolean) method.
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:
Figure 1: Gamma probability density function
The standard gamma probability density function is:
Figure 2: Standard gamma probability density function
When alpha = 1, GammaDist returns the exponential distribution with:
Figure 3: Equation
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.