[R-sig-ME] Distributional assumptions + case studies (was: Random or Fixed effects appropriate?)
Reinhold Kliegl
reinhold.kliegl at gmail.com
Thu Apr 10 17:51:36 CEST 2008
Hi Andrew,
The manuscript (Kliegl, R., Masson, M.E.J., & Richter, E.M. (2007).
Fixed and random effects of word frequency and masked repetition
priming: A linear mixed-effects model perspective) is available as PDF
at the top of my publications page here:
http://www.psych.uni-potsdam.de/people/kliegl/personal/pubs-e.html
I will send you a LaTeX version later this week. What all do you need?
For case studies, it may make sense to include data and R-scripts. Is
this your plan?
My co-authors and I realize that the manuscript is in need of an
overhaul with respect to the precision of some of the arguments
(especially with respect to justifications of data
transformation--another red herring in experimental psychology, aside
from p-values); we already have a very helpful set of reviews from a
first submission. Not sure yet, where we will go next with it.
Suggestions?
Thanks and all the best,
Reinhold
On Thu, Apr 10, 2008 at 12:06 AM, Andrew Robinson
<A.Robinson at ms.unimelb.edu.au> wrote:
> >
> > In analyses of reaction times (using subjects and items as crossed
> > random factors; carried out with Mike Masson and Eike Richter, 2007),
> > model-based estimates of correlations among random effects revealed
> > "clearer" patterns than the correlations between means and effects
> > computed for each subject (as they should, given that they were
> > corrected for unreliability). Unlike for fixed-effects estimates,
> > however, estimates of correlations among random effects were quite
> > susceptible to violations of distributional assumptions for the
> > residuals--up to a change in the sign of the correlation!
>
> This is a very interesting observation, and one that I suspect should
> not be buried in an email. Can you tell us more about it? In my
> workshops, I spend a lot of time focusing on the use of diagnostics to
> check distributional assumptions. It would be fabulous to be able to
> identify a case study in which getting the distributional assumptions
> was so clearly important.
>
> More generally, I wonder if it might be worth collecting such a set of
> case studies with clear and thorough analyses and wrapping them in a
> document. It seems to me that it would answer the request made by
> Iasonas Lamprianou recently.
>
> I'd be happy to coordinate such an effort, so long as the
> contributions were in LaTeX and Sweave. I know my students would
> benefit from it :)
>
> Is there any interest in such an idea, from potential conributors or
> (equally importantly) potential users?
>
> Cheers
>
> Andrew
>
>
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