st: a question about areg with robust versus areg with robust and cluster options

["maria gesheva" <m_gesheva@hotmail.com>]

Hi,

When looking through the stata help I came over the following FAQ:
''Why is it dangerous to use the robust cluster() option on areg? (areg 
estimates the same fixed-effects model as xtreg, fe)'' but the content had 
been removed.

I would like to ask the same question plus a related one: when is it 
appropriate to use areg only with the robust option and when areg with both 
robust and cluster options. (using bith options gives wider standard errors 
and this changes the set of variables that are significant so it does matter 
whether one uses only the robust or both the robust and the cluster 
options.)

Thank you in advance.

Maria

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