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This raises issues on a lot of fronts, I am afraid. For the treatment effect you may want to start with http://www.stata-journal.com/article.html?article=st0136
Have you also thought about -anova-? BTW, your command is probably: -xi: regress birthweight i.disease i.parity i.gestationalage, robust- ?
HTH
Martin
-----Ursprüngliche Nachricht-----
Von: [email protected] [mailto:[email protected]] Im Auftrag von Ali Khashan
Gesendet: Freitag, 6. Februar 2009 14:28
An: [email protected]
Betreff: 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
Thanks
Ali
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