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st: R: linear regression with robust variance estimation

From   "Carlo Lazzaro" <>
To   <>
Subject   st: R: linear regression with robust variance estimation
Date   Fri, 6 Feb 2009 16:40:35 +0100

Dear Ali,
I suppose that with robust you mean clustered robust on mother (the
principal sample unit, as it would seem for the outline of your data set).

Such an issue is covered in the very helpful Svend Juul's textbook An
Introduction to Stata for Health Researches. First edition. College Station:
Stata Press, 2006: 204-207.

If I recall correctly, a second edition of this textbook is now available.

Kind Regards,

-----Messaggio originale-----
[] Per conto di Ali Khashan
Inviato: venerdì 6 febbraio 2009 14.28
Oggetto: st: linear regression with robust variance estimation

Dear all,

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

Any advice is appreciated



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