WorksheetFunction.Gamma_Dist(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 Gamma_Dist(double Arg1, double Arg2, double Arg3, bool Arg4);public double Gamma_Dist (double Arg1, double Arg2, double Arg3, bool Arg4);Public Function Gamma_Dist (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, Gamma_Dist returns the standard gamma distribution.
- Arg4
- 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.
Returns
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:
Figure 1: Gamma probability density function
The standard gamma probability density function is:
Figure 2: Standard gamma probability density function
When alpha = 1, Gamma_Dist returns the exponential distribution with:
Figure 3: Equation
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.