On Jul 14, 2009, at 8:09 AM, Suresh Krishna wrote:
Hello,
I have a hierarchical dataset of this form and am trying to analyze
it in R.
1 subject
Tested under 2 conditions: A and B
10 sesssions in each condition
In each session, 2 kinds of tests: Test 1 and Test 2
200 independent repetitions of each test-type, with 200 Yes/No answers
So I think this is a 2 x 2 x 10 x 2 setup
What I want to know is whether the difference in percentage of yes
answers between Test1 and Test2 is different for the 2 conditions A
and B. I guess I could also state this as looking for an effect at
the highest stratum, after correctly pooling over all the lower
strata... i.e. Is there an "interaction" between the Effect of
Condition and the Effect of Test.
I looked through Agresti and Pinheiro/Bates and couldn't find an
example covering this situation. I would be really grateful if you
could suggest a way to go about this analysis in R, or a place where
I could read about this.
I considered:
Pool data from all the sessions for a given condition and test
together, thus getting 2000 repetitions of Test1 and Test 2 in each
condition. Now I have a 2x2x2 setup, which maps on to something in
Agresti, but then I am ignoring within-session correlation
information.
I could simply get a difference between Test1 and Test2 percentages
for each session, and then compare the distribution of these
differences in conditions A and B (with something like a t-test),
but then I only have 10 points (one for each session) and so I guess
I am throwing away a lot of information.
Very best,
Suresh
You are likely going to want to look at using glmer() in the 'lme4'
CRAN package by Doug and Martin. This functionality post-dates P&B.
There is a R-sig-mixed models list where you are likely better off
pursuing your query further, as there you will avail yourself of
experts in the field, including the package authors.
More information on that list is here:
https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
HTH,
Marc Schwartz
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
