[R-sig-ME] Zhang 2011 (re)analysis

[Ben Bolker]

  There's a fairly recent paper by Zhang et al (2011) of interest to
folks on this list

DOI: 10.1002/sim.4265

  In response to a post on the AD Model Builder users' list, I took a
quick shot at re-doing some of their results (they have extensive
simulation results, which I haven't tried to replicate yet, and an
analysis of binary data from Davis (1991) which is included (I *think*
it's the same data set -- the description and size of the data set match
exactly) in the geepack data set).

  If anyone's interested, my results so far are posted at

http://glmm.wikidot.com/local--files/examples/Zhang_reanalysis.Rnw
http://glmm.wikidot.com/local--files/examples/Zhang_reanalysis.pdf

  So far the R approaches I've tried agree closely with each other and
with glmmADMB (except MASS::glmmPQL, which I expected to be different --
the rest all use either Laplace approx. or AGHQ).  They *don't* agree
with the results Zhang et al got, yet -- I'm sure there's something I'm
missing in the contrasts or otherwise ...

  Suggestions or improvements are welcome.

  cheers
    Ben Bolker