difference in difference models in panel data difference based model why do we run an ols when do i expect equivalence of a panel ols difference in difference model when should we expect the difference in difference model to be equal to the equivalent panel model difference in difference model of treatments what model to run after treatment why can't i calculate the difference in the panel? why run difference in difference how to calculate the difference in treatment in data what model should we run to infer difference in difference why do researchers use stata for difference-in-difference difference-in-the-difference ols when exactly to expect equivalence? difference-in difference in a panel what is difference in difference difference in difference difference in difference data model how to infer the difference between treatments