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From |
Dana Chandler <dchandler@gmail.com> |

To |
statalist@hsphsun2.harvard.edu |

Subject |
Re: st: areg vs xi reg vs xtreg vs what else? |

Date |
Thu, 17 Sep 2009 09:22:18 -0500 |

Maarten - Thanks for your reply. Are you sure that I cannot use log_population? I may have been unclear in my description. I should have emphasized that my log_population is constant for each state and refers only to the log_population before my study. Hence it's really log_population_1940. Also, I'm then interacting it with grade-year combinations so that for example, I estimate a coefficient that describes the effect of log_population in 1940 on say, 6th graders in 1952. I think I am still identified if I have that interaction term. Best, Dana On Thu, Sep 17, 2009 at 8:56 AM, Maarten buis <maartenbuis@yahoo.co.uk> wrote: > --- On Thu, 17/9/09, Dana Chandler wrote: >> I'm running a large fixed effects model where each >> observation is a test score for every grade level, year, >> and state. My outcome variable is a test score and the >> focal independent variable is the % of HH in state that >> have cable television. The only other variable I have is >> log_population for the first year of my study at the state >> level which I also want to interact with each combination >> of grade-year. > > Are your fixed effects States? In that case you can't use > your log_population variable, as that is constant within > states. The whole point of fixed effects, as that you > control for all variation (observed and unbserved) that > remains constant within a state. The price you pay is > that you cannot study what these constant variables do. > You can do so, if you are willing to do a random effects > model. But now you have to assume that the remaining > unobserved state level variables are uncorrelated with > any of the observed variables. There is a huge difference > between disciplines in the willingness to accept this > assumption. > > hope this helps, > Maarten > > -------------------------- > Maarten L. Buis > Institut fuer Soziologie > Universitaet Tuebingen > Wilhelmstrasse 36 > 72074 Tuebingen > Germany > > http://www.maartenbuis.nl > -------------------------- > > > > > > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/statalist/faq > * http://www.ats.ucla.edu/stat/stata/ > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**References**:**st: areg vs xi reg vs xtreg vs what else?***From:*Dana Chandler <dchandler@gmail.com>

**Re: st: areg vs xi reg vs xtreg vs what else?***From:*Maarten buis <maartenbuis@yahoo.co.uk>

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