Subgroup-Analysis

[Pascal Hofmann]

Hello,

I have some problems executing a subgroup analysis in stata. I want to check the differences in treatment effects between a variable with 5 different levels.
So i want to check whether there is a significant difference between different educational level on my outcome variable.
I have already generated dummyvariabels for each education level. Now I have problems to find the differences between these groups in one regression.

For example:
Outcome: income
Treatment indicator variable (dummy): treat
Group variable (dummy, 1 if female, 0 if male): female
First step:
reg income treat if female==0
reg income treat if female==1
Second step:
gen femtreat=treat*female
reg income treat female femtreat

That example is just two groups (male,female) and I want to do the same for 5 different groups and i do not know how I execute it in stata.

So please help me, I'm lost!

[Joseph Coveney]

regress income i.treat##i.educational_level
testparm i.treat#i.educational_level

Oh, and skip "First step"

[Pascal Hofmann]

Okay thank you for that advise! But this is just the effect of educational level 1 on the other ones, or not? And I also want to get the effect of every educational level on the others (for example level 2 on 1,3,4,5).

And how do I interpret the values of the testparm command?

I hope you can help me!