to sci.stat.edu and SR Millis - On 29 Mar 2002 06:23:07 -0800, [EMAIL PROTECTED] (SR Millis) wrote:
> Thanks to Roy St Laurent & Rich Ulrich for their advice. In follow-up: > a reference for the Bradley-Blackwood procedure: > > Bradley, E & Blackwood, L (1989). Comparing paired data: a simultaneous > test of means and variances. Am Stat, 43, 234-235. By the way, I want to thank you again for that citation of Lin's concordance - "Lin has discussed the shortcomings of the t-test for assessing concordance between raters (Biometrics, 1989, 45, 255-268). Among other things, the paired t-test fails to detect poor agreement in [ ... ] " The article, and the measures, are better than I expected: this C_b measure of accuracy *does* have a potential advantage over the t-test, since it weighs in those variances. The article draws on some appropriate examples which are different from the ones that I have ever been concerned with. That is, there are examples with machine-measures, where the r's are (say) over 0.90. I look at t-test and correlations as important pieces of information in training or assessing human raters using subjective scales, with a focus on improving the positive information. The article looks as concordance as the single, summary measure for selection of an alternative, or approval of a device, with a focus on the combined errors, which are small. So it is not just editors (who I mentioned before) who need one measure, instead of using two, separately. So, I will try to keep Lin's coefficient in mind in the future. And he provides a formula for multiple raters. His measure of accuracy may be important by itself, too. Further notes to myself: check on the articles in google about further developments; pay attention to asymptotic behavior, for smallest N and for dichotomous measures. -- 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/ . =================================================================
