[R-sig-ME] New to LMER with 2 (easy?) questions...

Ben Bolker bolker at ufl.edu
Fri May 22 01:46:54 CEST 2009

  what I meant was, that if your blocks within sites were labeled
uniquely as 1,...,n*N you should specify your (block "within" site)
effect as (1|BLOCK), whereas if they were labeled 1,..,n,1,..,n,1,..,n
... you should specify it as (1|SITE:BLOCK) as Rolf did.  If your
blocks are labeled uniquely and you specify (1|SITE:BLOCK) then you
end up with a lot of empty SITE:BLOCK combinations (because e.g.
block 72 only occurs in site 14, but your model includes terms for
block 72 in every site).
  I hope that's now clear and that I'm right, but please correct
me if necessary!


Hank Stevens wrote:
> Ben,
> Did you mean it like this? I was under the impression it was the other
> way around ... .
> Hank
> On Wed, 2009-05-20 at 23:12 -0400, Ben Bolker wrote:
>>    The only thing I would check for is that your BLOCK numbers
>> are truly "nested" within SITE, i.e. that your blocks are numbered
>> 1..n within each site, not 1:(n*N) (where n = # blocks per site,
>> N = # of sites).  What are n and N?  A common cause of low estimated
>> block variance is low replication ...

Ben Bolker
Associate professor, Biology Dep't, Univ. of Florida
bolker at ufl.edu / www.zoology.ufl.edu/bolker
GPG key: www.zoology.ufl.edu/bolker/benbolker-publickey.asc

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