[R] zero random effect sizes with binomial lmer

[Dieter Menne]

Daniel Ezra Johnson <johnson4 <at> babel.ling.upenn.edu> writes:

> 
> I am fitting models to the responses to a questionnaire that has
> seven yes/no questions (Item). For each combination of Subject and
> Item, the variable Response is coded as 0 or 1.
> 
> I want to include random effects for both Subject and Item. While I
> understand that the datasets are fairly small, and there are a lot of
> invariant subjects, I do not understand something that is happening
> here, and in comparing other subsets of the data.
> 
> In the data below, which has been adjusted to show this phenomenon
> clearly, the Subject random effect variance is comparable for A
> (1.63) and B (1.712), but the Item random effect variance comes out
> as 0.109 for B and essentially zero for A (5.00e-10).
...

Check the list archives for quite a few postings of Professor Brian Ripley on
the subject of Hauk-Donner.


Dieter