[R-sig-ME] zero variance and standard deviation in random effects

[Rolf Turner]

On Tue, 2 Nov 2021 11:20:25 -0400
Ben Bolker <bbolker using gmail.com> wrote:

<SNIP>

> -- it's just hard to estimate variance reliably from a sample of
> three. (See
> https://rpubs.com/bbolker/4187
> for some simulated examples.) One standard approach to this problem
> is to treat province as a *fixed* effect.

<SNIP>

To me it makes little or no sense to treat "province" as a random
effect in any case.  Conceivably Alberta, Saskatchewan and Manitoba
could have been chosen at random from the 10 provinces, but it sure
doesn't look like it.  Moreover drawing inferences about the
"population of provinces" (which is the whole idea of random effects)
would be highly dubious, given the completely different nature of (e.g.
PEI) from the three prairie provinces in the "sample".

The data set involves the three prairie provinces; inferences drawn can
really only apply to those provinces.  Ergo "province" is a fixed
effect.

cheers,

Rolf Turner

-- 
Honorary Research Fellow
Department of Statistics
University of Auckland
Phone: +64-9-373-7599 ext. 88276