--- Gao Liu <[email protected]> wrote:
> some may still argue that some state-wide effects may never be
> observed but have significant impacts.
To follow up: notice that you are moving away from empirical sience
into the world of blind speculation (I am being a bit harsh) by trying
to control for things that are inherently unobservable. You have to
realize where the information comes from: it is either from the
observations, or through a smart design (e.g. randomized experiment),
or your imagination (we usually call that assumptions). So any
controlls for unobserved effects outside a smart design tells more
about what is going on in the researchers head than about what is going
on in the world. I am not trying to cyber spank you, I am just inviting
you to be sceptical of any solution anyone may offer you (including my
earlier solution of using a random effects model).
Hope this helps,
Maarten
-----------------------------------------
Maarten L. Buis
Department of Social Research Methodology
Vrije Universiteit Amsterdam
Boelelaan 1081
1081 HV Amsterdam
The Netherlands
visiting address:
Buitenveldertselaan 3 (Metropolitan), room Z434
+31 20 5986715
http://home.fsw.vu.nl/m.buis/
-----------------------------------------
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