sysuse nlsw88, clear drop if race == 3 gen byte b = race == 2 gen byte w = race == 1 gen bXmarried = b*married gen bXnever_married = b*never_married gen wXmarried = w*married gen wXnever_married = w*never_married qui reg hours b w bX* wX*, nocons sheafcoef, latent(b_marst: bXmarried bXnever_married if b ; /// w_marst: wXmarried wXnever_married if w ) post test [main]_b[b_marst] = [main]_b[w_marst]