[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:


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.

Thanks and all the best,

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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