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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