[R-sig-ME] random factor variance

[Ken Beath]

On 20/05/2009, at 11:43 AM, João R. wrote:

> Hello,
> I have recently used lme4 package to run a glmm, but a get 0 variance
> explained by the random effect. The model has 5 fixed effects, and I  
> have
> run each of them separately and for two of them (F1, F3) I also get 0
> variance for the random effect. Do you have any ideas of what might be
> causing this? Is this kind of result to be expected?
> thanks
>

This means that the variance of the random effect needed to explain  
your data is zero.  The clusters vary by the same amount or less than  
if there was a random effect, that is they can all be explained by  
subject variation.

Ken


>
> Generalized linear mixed model fit by the Laplace approximation
> Formula: DV ~ F1 + F2 + F3 + F4 + F5 (1 | R1)
>   Data: JD
>   AIC   BIC logLik deviance
> 203.2 225.9  -94.6    189.2
> Random effects:
> Groups Name        Variance Std.Dev.
> R1  (Intercept)  0        0
> Number of obs: 190, groups: R1, 14
> Fixed effects:
>            Estimate Std. Error z value Pr(>|z|)
> (Intercept)   1.8949     1.1869   1.596  0.11039
> F1          4.6740     2.4365   1.918  0.05507 .
> F2         -2.0657     0.7543  -2.739  0.00617 **
> F3       21.8036     8.8890   2.453  0.01417 *
> F4   1.0968     0.4874   2.250  0.02444 *
> F5      -1.7430     0.9583  -1.819  0.06894 .
>
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