On Tue, 26 Mar 2002 21:49:08 +0000 (UTC), "JP" <Janepeutrell@removethis bit.btinternet.com> wrote:
> I have been unable to find an adequate explanation of exactly what is the > difference between an interclass and in intraclass correlation, and the > circumstances in which you would choose either. For the 'intraclass correlation', you *assume* that the means have the same mu. It can be computed for a *set* of raters. Deviations are computed around the common mean. Thus, you only use it for 2 ratings when you expect equality, with parallel measurements. The intra-class is what is possible, when you can't systematically "distinguish" the raters in a fair way. For contrasting 2 raters, I like using a paired t-test and the corresponding interclass correlation. That shows you both the main pieces of information, without confusing them or confounding them at all. You get r to measure parallelism; you get t to measure mean-difference. (What you don't have assured is the equal-variances, which presumably isn't much of a problem.) -- Rich Ulrich, [EMAIL PROTECTED] http://www.pitt.edu/~wpilib/index.html . . ================================================================= Instructions for joining and leaving this list, remarks about the problem of INAPPROPRIATE MESSAGES, and archives are available at: . http://jse.stat.ncsu.edu/ . =================================================================
