On Thu, 10 Oct 2002 14:05:08 +0200, Jan Malte Wiener <[EMAIL PROTECTED]> wrote:
> hi, > hopefully a simple one -> > > let's assume i have data like this: > subject A: 1,0,1,1,0,1,1,1 -> mean=6/8=0.75 > subject B: 1,1,1 -> mean=3/3=1 > > weighted arithmetic mean of A+B-> (8*0.75 + 3*1)/11 = 0.82 > -> well that was easy, but what if i do have 20 subjects like this and i > want to compare their weighted arithmetic mean to the weighted mean of > another group of 20 subjects ?? i guess i need to weight every single > subject-mean before running any stat-test. and here is my problem: how > do i weight the individual subject means ?? Statistically speaking, that looks bad. You don't have this problem when comparing 20 vs 20 subjects, if you are doing an Analysis of variance in the usual, legal, legitimate way; you want to count each Subject once. Weighting creates a problem of logic in computing 'error'; it is a problem of whether the analysis is by ANOVA. If you still want to get the weighted average that you describe, use "WEIGHT" . If you want to do test on samples with weighted Subjects, you need to "bootstrap." Read your manual or help file for WEIGHT. Check friendly SPSS sites for examples of bootstrapping. -- 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/ . =================================================================
