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Re: st: 3-level model for crime victimization


From   Joerg Luedicke <joerg.luedicke@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: 3-level model for crime victimization
Date   Tue, 25 Sep 2012 10:59:52 -0500

If there are 8 neighborhoods in 1 city then the level-3 sample size
would be 1! As a result you would throw a bunch of constants in your
model which does not make sense. Besides, a level-2 sample size of 8
is very small (at least for the standard likelihood based methods) and
is usually problematic with respect to point and variance estimates of
the fixed effects as well as the varying intercept/coefficient
variation. I believe this is discussed in any multilevel textbook.

Joerg

On Tue, Sep 25, 2012 at 10:45 AM, JVerkuilen (Gmail)
<jvverkuilen@gmail.com> wrote:
> On Tue, Sep 25, 2012 at 9:41 AM, Erik Alda <erik.alda@gmail.com> wrote:
>> Dear Statalisters
>>
>> I am running a, so far, 2 level model on crime victimization using a survey
>> of 8 neighborhoods in a large city in Brazil. The firs level is individual
>> level predictors and the second level is neighborhood level predictors.
>> Since the survey is not representative of the whole municipality, would I be
>> able to include a 3rd level with citywide variables to estimate the effect
>> of policy?
>
> I don't see why you can't include it though your level 3 N is somewhat
> small. As long as the sample sizes per neighborhood aren't reasonably
> even it should run OK, though. The fact that the survey isn't
> representative is a study limitation and affects what conclusions you
> can draw from it, but that's separate from whether there's level 3
> heterogeneity in the sample you do have. In some cases having the
> external generalizability of a a representative sample is mandatory.
> In other case it's not.
>
>
> --
> 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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