On 12 May 2004 06:37:30 -0700, [EMAIL PROTECTED] (Paul R Swank) wrote: > And doing a Pearson Coorelation and a t-test doesn't tell you the overall > impact of the error.
If the t-test is *not* relevant, which may be true for test-retest, the Pearson can be a more proper measure of impact than the ICC which slightly decreases the reported score. - there are extra issues for your study if the variances are should not be pooled, for any choice of coefficient. If the t-test *is* relevant, it can be a warning of a grievous impact, all by itself; and that warning is generally masked by reporting an ICC which may be only slightly less than the Pearson r. Those are two reasons why the two tests together are better for *examining* your data, than looking at ICCs. Yes, it is the overall impact, and that can be useful for the *final* statement, especially when a very precise statement of overall impact is warranted -- because, for instance, power analyses are being based on the exact value of the exact form of ICC that is needed: Same versus different raters; single versus multiple scorers. And I think it is an over-generalization to prefer an ICC when the issue is the cruder one of apparent adequacy. The ICC is less informative (about means) and less transparent (multiple versions available to select, all of them burying the means). [snip, rest] -- 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/ . =================================================================
