[R-sig-ME] crossed random effects example

[Gabor Grothendieck]

The values are the same to one decimal place and nearly the
same to two decimal places.

On Sun, Mar 1, 2009 at 11:12 AM, Jeroen Ooms <j.c.l.ooms at uu.nl> wrote:
> Hello Gabor,
>
> I don't understand what you mean. lmer reports a variance of treatment
> that is practically 0:
>
> Random effects:
> Groups    Name        Variance   Std.Dev.
> airport   (Intercept) 1.0369e-01 3.2202e-01
> treatment (Intercept) 1.0140e-23 3.1844e-12
> Residual              4.6991e-02 2.1677e-01
>
> It seems as if lmer shows there is no variance at all for the
> treatment effect. I think this is quite different than the 0.04
> reported in the slide. Are you sure I did not did use the correct
> syntax?
>
>
>
> On Sun, Mar 1, 2009 at 4:27 PM, Gabor Grothendieck
> <ggrothendieck at gmail.com> wrote:
>> I suspect that the slide you are referencing mislabeled the
>> standard deviations as variances since there is reasonable
>> correspondence between your output and the slides if that
>> were the case.
>>
>> Also check out:
>> http://www.stat.columbia.edu/~gelman/arm/examples/pilots/
>>
>> On Sat, Feb 28, 2009 at 6:00 PM, Jeroen Ooms <j.c.l.ooms at uu.nl> wrote:
>>> I am trying to learn about crossed random effects modeling in lme4. I
>>> found this presentation that provides a small crossed dataset.
>>> http://www.biostat.jhsph.edu/~fdominic/teaching/bio656/lectures/5addsin.crosslevels.ppt
>>> I would like to reproduce the variance components as reported on slide
>>> 9 of the powerpoint. Here is my code:
>>>
>>> y <- c(0.38,0,0.38,0,.33,1,.12,1,.25,0,.5,.12,.5,1,.12,.86,.5,.67,.33,0,.14,1,0,1,.14,0,.71,0,.29,1,.14,1,.43,0,.29,.86,.86,.86,.14,.75)
>>> x2 <- rep(paste("airport",1:8,sep=""),5)
>>> x1 <- rep(paste("treatment",1:5,sep=""),rep(8,5))
>>> mydata <- data.frame(y=y,airport=x2,treatment=x1)
>>> lmer(y~1+(1|airport)+(1|treatment),data=mydata)
>>>
>>> However, the variance components as reported by lmer are different
>>> from the ones in the slides. What formula should I use? thank you!
>>>
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>>> https://stat.ethz.ch/mailman/listinfo/r-sig-mixed-models
>>>
>>
>