# Interaction with dummies [duplicate]

I have a question about econometrics in general. If I have a regression with an interaction between two dummies, do I need to have those dummies separated in the regression too.

I have this regression: is this right?

$$y_i=\beta_0 + \beta_1d\_sex_i*d\_country_i +\beta_2d\_country_i + \varepsilon_i$$

or do I need to do this:

$$y_i=\beta_0 + \beta_1d\_sex_i*d\_country_i +\beta_2d\_country_i + \beta_3d\_sex + \varepsilon_i$$

• This has been asked and answered many time. You should include the main effects along with the interaction. See here – Robert Long Oct 22 '20 at 18:34