Dear all,

I want to perform a difference of means test on my dataset, to see whether there is a difference in the means of the treated and control group. With the Stata command

foreach var of varlist _Assets _Ebit _Revenue {
ttest `var', by(published)
}

I could already get a first intuition. However, I would like to "group" these data on a firm level. Is there a why to perform the same test clustered at the firm level.
I have a unique identifier (ISIN).

Any suggestions are highly appreciated

Best

Jannik