# Inverse Chi Square?

1. May 4, 2012

How can I determine what the smallest value of a χ2 statistic must be to reject the null hypothesis at α = 5%, for a distribution with 9 degrees of freedom? Thanks in advance.

2. May 5, 2012

### SW VandeCarr

It's not clear from your question whether you asking about the inverse chi square distribution or simply asking about how to determine the correspondence between the chi square value and alpha.

In the first case, there are two definitions of the inverse chi square distribution. One is the chi square of 1/X for $\nu$ degrees of freedom and the second is the chi square of $\nu / X$ for $\nu$ degrees of freedom.

3. May 5, 2012

### chiro

Hey MadViolinist and welcome to the forums.

Following on from what SW VandeCarr said, do you know the PDF of the distribution you are working with (chi-square if you are using a chi-square statistic) and how you solve (using a numerical routine) the value of a cumulative probability?

4. May 5, 2012