[R-sig-ME] Question on random effect

[Ben Bolker]

Yes, the assumption is that the random effects are (conditionally)
independent.  It can help to specify covariates  (such as
latitude/longitude or eastings/northings, or environmental conditions
[temperature, elevation, etc.]) for sites to mop up some of the
independence. It is theoretically possible, although I don't know of
an easy off-the-shelf way to do it, to impose (e.g.) spatial
correlation structures at the level of the random effects ...  or you
could examine the spatial dependence of the conditional modes/random
effects and try to convince yourself it was weak ...

On Tue, Jul 11, 2017 at 7:14 AM, Joaquín Aldabe
<joaquin.aldabe at gmail.com> wrote:
> Hi all, when working with mixed models, do the levels of the random effect
> have to be independent? For example, if my random effect is the identity of
> sites and it is associated to the intercept, do sites have to be
> independent?
>
> I appreciate comments and bibliographic references.
>
> Thank you very much in advanced,
>
> Joaquin
>
> --
> *Joaquín Aldabe*
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>
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