Re: st: When number of regressors greater than the number of clusters in OLS regression

[Steven Samuels <sjhsamuels@earthlink.net>]

I just sent another post, Divya, before I received this one.  Were  
all districts in the 17 states included or only a sample?   If you  
want to describe only the 17 states, then I am quite sure that you  
need not designate state as a cluster variable.  This will give you  
room for a sufficient number of regressors. Please give information  
on what you mean by "district level"--does that mean you have no data  
for individual households?

Regards,

Steven Samuels


On Sep 1, 2008, at 4:09 PM, Divya Balasubramaniam wrote:


> Hello Dr. Steven,
>
> I chose the states based on availability of data. Yes, all the  
> districts are part of the 17 states only. Any other suggestions  
> will really help.
>
> Thanks,
>
> Divya.
> =======================================
> Divya Balasubramaniam
> Economics PhD Student
> Terry College of Business
> University of Georgia
> Athens -30602.
>
> From: Steven Samuels <sjhsamuels@earthlink.net>
> Date: September 1, 2008 1:05:39 PM EDT
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: When number of regressors greater than the number  
> of clusters in OLS regression
> Reply-To: statalist@hsphsun2.harvard.edu
>
>
> More basic questions, Divya:  What is your target population:  the  
> 17 states (of India, perhaps?) or the entire country?  Were the 17  
> states selected from all states by a sampling process?  Or were  
> they chosen in some other way--for example, because they had data  
> available.  Are all districts from the selected states in your sample?
>
>
> -Steven
> On Sep 1, 2008, at 12:35 PM, Divya Balasubramaniam wrote:
>
>
> > Dear Dr.Schaffer,
> >
> > I am using clustering in my analysis and I am having some trouble  
> > understanding some of the important issues. I have read several  
> > papers you have written on clustering issues and hence I am  
> > emailing you to seek help.
> >
> > I am doing a district level analysis for the census year 2001. I  
> > have 436 districts in total coming from 17 States. I run an OLS  
> > regression of Share of households having tap water access on  
> > several controls variables (I have about 25 Regressors).  I use  
> > the STATA command areg Y on X, absorb(State) cluster(state). I  
> > have the state fixed effects and clustered by State.
> >
> > My question is: I have more regresors(25) than the number of  
> > clusters(17). I also find in the STATA output that I have F-stat  
> > missing. I would like to seek your advice on whether I can make  
> > inference by looking at the individual coefficient estimates and  
> > the reported robust Standard errors. I did see your comment on  
> > this issue on the STATA listserv. However, I could not find  
> > answers as to how to fix this problem of having more regressors  
> > than the number of clusters.
> >
> > I will be extremely thankful if you can kindly help me in this  
> > regard.
> > Sincerely,
> > Divya.
> > =======================================
> > Divya Balasubramaniam
> > Economics PhD Student
> > Terry College of Business
> > University of Georgia
> > Athens -30602.
> > *
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