GAMMAINV Function

Basic Description

The Excel Gammainv function returns the inverse of the Gamma Distribution.

Syntax: GAMMAINV( probability, alpha, beta )

where the function arguments are:

probability The probability value for which you want to evaluate the inverse gamma distribution (must be between 0 & 1)
alpha A parameter of the distribution
beta A parameter of the distribution
Note: if beta=0, then this specifies the Standard Gamma distribution

 

Gammainv Function Example

The charts below show the Cumulative Gamma Distribution and the Inverse Cumulative Gamma Distribution, with the parameter alpha set to 3 and the parameter beta set to 2.

Plot of the Cumulative Gamma Distribution Function with α = 3 and β = 2

Cumulative Gamma Distribution Function with α=3 & β=2
Plot of the Inverse Cumulative Gamma Distribution Function with α = 3 and β = 2

Inverse Cumulative Gamma Distribution with α=3 & β=2

If you want to calculate the value of the Inverse Cumulative Gamma Distribution for the probability 0.5, this can be done using the Excel Gammainv function, as follows:

=GAMMAINV( 0.5, 3, 2 )

This gives the result 5.348120627.

 

Gammainv Function Errors

If you get an error from the Excel Gammainv function this is likely to be one of the following :

#NUM! Occurs if either the supplied probability value is < 0 or ≥ 1 or the supplied alpha ≤ 0 or the supplied beta ≤ 0
#VALUE! Occurs if any of the supplied arguments are not recognised as numeric values
#N/A Occurs if Excel fails to converge to a solution after 100 iterations. Excel is unable to calculate the solution.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

*

code

clearPost Comment