Hi,
I have longitudinal binary responses from a clinical trial. I am fitting the following random effects model in lme4::glmer.  The model is estimated without any problems.  However, I get an error when I try to compute the confidence intervals using the profile likelihood.  Does not the profiling approach work for more than one random effect?  Can someone point  out the problem?
Thanks,
Ravi

summary(mod2 <- glmer(imps79b ~ tx + sweek + (sweek|id), data=schiz, family=binomial))

Generalized linear mixed model fit by maximum likelihood (Laplace Approximation) ['glmerMod']
Family: binomial  ( logit )
Formula: imps79b ~ tx + sweek + (sweek | id)
   Data: schiz

     AIC      BIC   logLik deviance df.resid
  1259.4   1291.7   -623.7   1247.4     1597

Scaled residuals:
     Min       1Q   Median       3Q      Max
-3.03973  0.00912  0.04957  0.21372  1.45395

Random effects:
Groups Name        Variance Std.Dev. Corr
 id     (Intercept) 13.993   3.741
        sweek        4.093   2.023    -0.65
Number of obs: 1603, groups:  id, 437

Fixed effects:
            Estimate Std. Error z value Pr(>|z|)
(Intercept)   9.1994     1.3105   7.020 2.22e-12 ***
tx           -2.5075     0.5996  -4.182 2.89e-05 ***
sweek        -3.1344     0.4503  -6.960 3.40e-12 ***
---
Signif. codes:  0 '***' 0.001 '**' 0.01 '*' 0.05 '.' 0.1 ' ' 1

Correlation of Fixed Effects:
      (Intr) tx
tx    -0.786
sweek -0.922  0.537
>

# profiled confidence intervals
> confint(mod2, method="profile")
Computing profile confidence intervals ...
Error in zetafun(np, ns) : profiling detected new, lower deviance
In addition: Warning messages:
1: In profile.merMod(object, signames = oldNames, ...) :
  non-monotonic profile
2: In profile.merMod(object, signames = oldNames, ...) :
  non-monotonic profile
>


Ravi Varadhan, Ph.D. (Environmental Eng.), Ph.D. (Biostatistics)
Associate Professor,
Division of Geriatric Medicine & Gerontology
School of Medicine,
Johns Hopkins University
Ph: 410-502-2619
Email: ravi.varadhan@jhu.edu<mailto:ravi.varadhan@jhu.edu>
http://www.jhsph.edu/research/centers-and-institutes/johns-hopkins-center-on-aging-and-health/people/Faculty_personal_Pages/Varadhan.html


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