Repeated measures analysis of fractions summing to a constant

Posted by Kirill Orlov on Apr 04, 2013; 8:05am
URL: http://spssx-discussion.165.s1.nabble.com/Repeated-measures-analysis-of-fractions-summing-to-a-constant-tp5719257.html

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.