[R-sig-ME] Convergence failure with glmer().

[Rolf Turner]

This is kind of a follow-up to a question that I asked a few days ago 
with the subject line "Bernoulli glmm question".

[The responses to my question more-or-less confirmed that I was 
basically on the right track with my model and [g]lmer() syntax.
The suggestion (in retrospect "obvious") was made that I should include 
a "word" random effect in my model.  It was also suggested that I should 
include some interaction terms.  However no result "came back" after 
over an hour of waiting, so I killed the job and gave up on this.]

However --- yesterday, after a few hiccups, I installed the latest 
version of lme4 (version 1.1-5) from CRAN.

Now the model that I successfully fitted with my rather elderly version 
(cannot remember the version number; I *think* I could dig it up from 
backups if it is of any interest) of lme4 results in a warning:

> Model failed to converge with max|grad| = 0.0922338 (tol = 0.001)

I tried switching the optimizer to "Nelder-Mead" and got an apparently 
"even worse" warning:

> Model failed to converge with max|grad| = 0.150396 (tol = 0.001)

For the record, my call was:

fit <- glmer(y ~ sex+type+(1|student)+1|word),family=binomial,data=X,
              control=glmerControl(optimizer="Nelder_Mead"))

This is just a warning, not an error, but it does seem to indicate that 
the fit obtained is not (quite?) correct.

Is there anything that I can *do* about this?  I've tried reading the 
help files, but failed to discern anything useful in this regard.  I 
would appreciate suggestions.

If anyone is sufficiently interested, I can make the data set available 
to them.  It's a wee bit on the large side, but; 10314 records.

Thanks for any words of wisdom.

cheers,

Rolf Turner