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Re: st: Three level mixed random and crossed effects model


From   "JVerkuilen (Gmail)" <jvverkuilen@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Three level mixed random and crossed effects model
Date   Thu, 13 Sep 2012 09:00:31 -0400

On Wed, Sep 12, 2012 at 10:59 PM, Mrs Mohana Rajmokan <
mohana.rajmokan@uqconnect.edu.au> wrote:

> Dear List,
>
> I am trying to fit a 3 level random and crossed effects model to a
> continuous outcome to estimate the respective variance components of each
> level of the 3  (for doctors)
>
> <snip>

At first blush nothing appears wrong with your specification, though I
thought you needed to use the _all keyword in the specification of a
crossed random effect. I've not fit a level 3 model with crossed random
effect though.

General advice whenever fitting a complex model is to fit simpler ones
nearby even if you don't really want to interpret them. So I'd try ignoring
the third level to see how things go. In short, simplify the model to see
where things blow up when you add another level. You should also consider
turning difficult on (maximization options).

You don't say what your Ns at different levels are. If there aren't many
doctors that could create problems, but in that case you might well be
better off simply putting in dummies for them, even though it's not the
model you truly wanted to fit.

Jay
--
JVVerkuilen, PhD
jvverkuilen@gmail.com

"Out beyond ideas of wrong-doing and right-doing there is a field. I'll
meet you there. When the soul lies down in that grass the world is too full
to talk about." ---Rumi
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