Re: Repeated measures analysis of fractions summing to a constant

Posted by Bruce Weaver on Apr 04, 2013; 10:30am
URL: http://spssx-discussion.165.s1.nabble.com/Repeated-measures-analysis-of-fractions-summing-to-a-constant-tp5719257p5719259.html

Hello Kirill.  This is not a direct answer to your question.  I'm just pointing to a thread from a couple years ago that addressed the same question.  One of my posts in it gives a couple of references that may be of interest to you.  Both of them suggest that ANOVA generally works quite well with "ipsative" data (or "allocated observations").  You can see the relevant messages here:

   http://listserv.uga.edu/cgi-bin/wa?A2=ind1101&L=spssx-l&P=36237

HTH.

Kirill Orlov wrote

Consider you have a between-within design: several between-subject
groups and several (3 or more) repeated measures (= within-subject)
trials. It's all very classic and typical. The nuance, however, is that
the values for every subject sum across the repeated levels to a
**constant**. This is because the data are complementary, i.e.
percentages of fractions, so, in this case they sum to 100 for every
individual. For example, with 3 RM levels, a respondent's data is like
30%, 22%, 48% (sum=100); for another respondent 25%, 33%, 42% (sum=100).

I know that I can analyze between-groups X repeated-measures count data
via Generalized Estimating Equations procedure. By I doubt in this case
because the values *sum to a constant*, they are complementary
fractions; they are not counts of successes in repeated independent trials!

Can I analyze such data in SPSS and how? Thanks.