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gee, geese and glmer

2 messages · Ben Bolker, David Duffy

#
[forwarding a conversation about lme4/lme4.0 incompatibilities.  This
example looks pretty interesting, as it seems hard to prove that lme4
*isn't* giving the right answer/an answer that is numerically superior
to lme4.0, yet the lme4.0 answer is biologically preferable/more similar
to other estimation approaches.  I don't know yet if we will eventually
find out that (1) the data are weird in a way that explains the
difference; (2) lme4 is actually misconverging, preliminary evidence to
the contrary; (3) ???  Enlightening comments are welcome.]


-------- Original Message --------
Subject: RE: [R-sig-ME] gee, geese and glmer
Date: Tue, 18 Mar 2014 00:18:01 +0000
From: Yang, Qiong <qyang at bu.edu>
To: Ben Bolker <bbolker at gmail.com>, "Chen, Ming-Huei" <mhchen at bu.edu>
CC: 'lme4-authors at lists.r-forge.r-project.org'
<lme4-authors at r-forge.wu-wien.ac.at>

Hi Ben,
Thanks for be mindful about our data confidentiality- what we
communicated in this email sequence so far can be copied to the general
mailing list.

Just to clarify further: All the cases are singletons(i.e. families of 1
member) while controls are from extended families (i.e. families of
multiple members).

The predictor variables do not identify the cases from controls.
We fitted reduce model where the only predictor is sex which does not
identify cases from controls however still observed reversed sign on
beta coefficients between lme4 and other software:
First, let's look at crude case by sex table
        1    2
  0   2554 3021
  1    310  290
Ignoring family structure: Odds Ratio=0.79; beta=-0.23

Since all cases are singletons, I don't think including family-specific
random effects should change the direction of sex effects. Therefore I
tend to think the effect direction given by lme4 is not correct. Below
are the results with only sex as predictor.
list()
Estimate Std. Error    z value      Pr(>|z|)
(Intercept) -10.2359223  0.4644516 -22.038725 1.225388e-107
sex           0.3531757  0.1837722   1.921813  5.462931e-02
Warning message:
In mer_finalize(ans) : false convergence (8)
Estimate Std. Error    z value     Pr(>|z|)
(Intercept) -3.2807992  0.2868701 -11.436533 2.746424e-30
sex         -0.2592505  0.1629382  -1.591097 1.115877e-01
estimate     san.se      wald           p
(Intercept) -1.8742252 0.16010676 137.03271 0.000000000
sex         -0.2346185 0.09068416   6.69363 0.009675797
Estimate Naive S.E.    Naive z Robust S.E.   Robust z
(Intercept) -1.8742252 0.13510959 -13.871889  0.16010676 -11.706097
sex         -0.2346185 0.08601766  -2.727562  0.09068416  -2.587205

Thanks a lot, Qiong

-----Original Message-----
From: Ben Bolker [mailto:bbolker at gmail.com]
Sent: Monday, March 17, 2014 3:51 PM
To: Chen, Ming-Huei; Yang, Qiong
Cc: 'lme4-authors at lists.r-forge.r-project.org'
Subject: Re: [R-sig-ME] gee, geese and glmer


  [I'm not going to cc: to r-sig-mixed-models, as you may consider parts
of it to be sensitive, but I would like to ask permission to do so in
the future, as I think it would be useful to have these conversations in
public -- please let me know]
On 14-03-17 03:39 PM, Ming-Huei Chen wrote:
Possibly, although I would think the cohorts would have to be
identifiable somehow from the predictor variables.
slicetrans is a function from the bbmle package, but it turns out to
be un-exported (this is still rather experimental functionality), so you
would need to use bbmle:::slicetrans
This warning *might* be spurious (the lme4 maintainers have been
having a private conversation about the fact that one may get
false-positive warnings about gradients when the fit is singular):
t is weaker than Normal (i.e., for the same mean (typically 0) and
variance it has fatter tails).  However, there are two dimensions of
"weakness" -- to make a prior weaker you can make the scale (i.e.
variance) larger, and/or make the shape parameter more diffuse (i.e.,
make the tails fatter, in the sequence Gaussian (= t_\infty -> t_{large
n} -> t_{smaller n}).  (You may end up discovering that the results
depend on the strength of the prior ... which will open up interesting
cans of worms in terms of what the data are actually telling you ...)
#
On Tue, 18 Mar 2014, Ben Bolker wrote:

            
lme4 has got stuck. The setup as described is pretty pathological: a) sex 
is not usually correlated within families, and more significantly b) there 
are no families containing both cases and controls.  So, the variance for 
famid should be zero, and we should get the same answer as a binomial 
regression.

| David Duffy (MBBS PhD)
| email: David.Duffy at qimrberghofer.edu.au  ph: INT+61+7+3362-0217 fax: -0101
| Genetic Epidemiology, QIMR Berghofer Institute of Medical Research
| 300 Herston Rd, Brisbane, Queensland 4006, Australia  GPG 4D0B994A