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

[Steven Samuels <sjhsamuels@earthlink.net>]

Divya-

So, you have n = 436. Just remove State as a cluster variable and  
continue with your modeling. You won't be troubled by the limit on  
regressors again; just keep the number to <=44 (10% of observations).

Good luck!

-Steven Samuels

On Sep 1, 2008, at 4:22 PM, Divya Balasubramaniam wrote:


> Hello Dr. Steven,
>
> My dependent variable is:share of total number of households in a  
> district having access to tap water. (I have the district totals)
>
> 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 4:13:40 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
>
>
> Divya,
> I reread your question and realize that you probably do not have  
> sample data at all. The Census of India was not a sample at all,  
> but, ideally, was a 100% enumeration. (Just as in other countries,  
> this will not be perfectly true.) So, I am not sure that you should  
> be clustering on State, or even on district, for that matter.  
> Please reply with details about your observations. For example, do  
> you have information on individual households or just district totals?
>
> Regards,
>
> Steven
>
>
> On Sep 1, 2008, at 1:05 PM, Steven Samuels wrote:
>
>
> > 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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