comparison of measurements of two methods - determination of reliability

#1
The aim is to compare two measurement methods. Therefore with each method two consecutive measurements were performed on 25 subjects (so overall 4 x 25 measured values) The relevant parameter is an amplitude.

To determine the reliability of each method, the “interindividual coefficient of variation” and the ”re-test coefficient of variation” should be calculated. I don’t really understand the difference and what is expressed by these two coefficients?

Does it make sense to calculate the “Intraclass correlation coefficient” (ICC, two way mixed)? Is it the same as the “re-test-Coefficient of variation”?

How should I proceed?
 
#2
Hi,
Not sure I know the answer, Betty, but I have a few questions/ suggestions which may be helpful:

Are the two different tests performed on the same subjects?
Are the two tests performed at the same time?
Why have you done consecutive measures (has something changed within the subjects? Is it pre- and post- some event)?

I once compared two different results between consecutive patients and was advised to do intraclass correlation (this was for the same test performed in the same person at a different time period).

When looking at different tests and how they compare (i.e. the agreement) I have been advised to construct a bland-altman plot. Is this something you are looking at?