Statistics question.......?

Question

What test can you use to compare two Std deviations of two different methods to see which method is more precise? The DF values differ as well.

Answer 1

An F test is usually used.

The chain is as follows:

A normal squared is Chi squared
sum of Chi squares is Chi square
ratio of Chi squares is F test

You don't reall have the std deviations of the population, you have estimates based on observations from a normal, therefore you really have the sum of normals squared, or Chi-square.

Look into the F test. It tests the ratio of the estimates of variance, and has 2 df.