# How do i get critical value from F-table

The table given in the Schweser is at 5% and 2.5%. For example if α= 0.01 and 2-tailed test, df = 19, what would be the critical value. I can’t get aroung this concept

First, you don’t have a 1% table, so you cannot find the value.

Second, you need two degrees of freedom: one for the numerator and one for the denominator. You have only one, so you cannot find the value.

Sorry for the wrong data in previous post df for both numerator and denominator = 119

The curriculum has a table for α = 0.005 in the right tail. The closest degrees of freedom are 120 each, and the critical value is 1.61.

(If you use the Excel function F.INV.RT(0.005,119,119) you get 1.6087.)

@S2000magician Thanks a lot

My pleasure.

Just remenber to use the largest degree of freedom first when reading the table

What do you mean?

The degrees of freedom in the numerator run across the top of the table and the degrees of freedom in the denominator run down the left side. Sometimes the former is larger, other times the latter is.

Sorry, I made a silly mistake.

You can force the F test into a right tail test by placing the sample with the large variance in the numerator and the smaller variance in the denominator. It does not matter which sample has the larger sample size.

Exactly right.