st: re:linear regression with robust variance estimation

[Kit Baum <baum@bc.edu>]

<>	
Ali said
I have a small data set of 136 infants each 2 of them have the same  
mother. All mothers have a disease which I am at its effect on  
birthweight. These women were diagnosed and treated after giving birth  
for the first child. I am trying to measure the difference in mean  
birthweight between infants who were born before treatment and those  
who were born after treatment. At the same time I want to account for  
parity (3 categories 1, 2 or 3) and gestational age (4 categories).

I am using regress with robust option to account for the fact that the  
data is not independent. Is there a way to include the mothers  
personal number in the model? Or does robust take into this problem  
into account?

The model I used is x: regress birthweight i.disease i.parity  
i.gestationalage, robust


why not cluster(motherid) ? That subsumes robust and allows for error  
correlation among children of the same mother.

Kit Baum, Boston College Economics and DIW Berlin
http://ideas.repec.org/e/pba1.html
An Introduction to Modern Econometrics Using Stata:
http://www.stata-press.com/books/imeus.html


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