Chi-Square distribution question.

[Dam100]

I am trying to solve P(χ - upper 2, lower - 20 > say 20 or 25), I can't understand how to use a table to figure this out. Any advice?

 

[tkhunny]

I'm thinking you'll have to provide more information. [math]\chi^{2}_{20} > 25[/math]?

There should be a "Degrees of Freedom" indicator or index. That's what that "lower-20" means.

 

[Dam100]

I have attached some images showing the problem and solution, I can't understand where the 0.7986 value has come from, I believed the attached table is what I should be using as it is in the formula booklet and the only one for Chi-Square.

Thank you for your assistance.

 

[tkhunny]

Now, just read it.

1) Go down the left to the "20" column. This is 20 degrees of freedom.
2) On that row, go to the fight until you find 25, or the two values surrounding 25.
3) Linear Interpolation is usually sufficient to answer this sort of question.