GAMMADIST

Definition

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.

Sample Usage

Syntax 

GAMMADIST(x,alpha,beta,cumulative) 

The GAMMADIST function syntax has the following arguments: 

• X     Required. The value at which you want to evaluate the distribution.

• Alpha     Required. A parameter to the distribution.

• Beta     Required. A parameter to the distribution. If beta = 1, GAMMADIST returns the standard gamma distribution.

• Cumulative     Required. 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.

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.

In order to use the GAMMADIST formula, start with your edited Excellentable:

Then type in the GAMMADIST formula in the area you would like to display the outcome:

By adding the values you would like to calculate the GAMMADIST formula for, Excellentable will generate the outcome: