微观计量双重查分本页总览Difference-in-Differences Introduction Hypothesis linear trend assumption no effect on the control group parallel trend assumption Yit=β0+β1∗Treati∗Postt+β∗ΣZit+μi+τt+ϵit(1)Y_{it} = \beta_0 + \beta_1 * Treat_i * Post_t + \beta * \Sigma Z_{it} + \mu_i + \tau_t + \epsilon_{it} \quad (1)Yit=β0+β1∗Treati∗Postt+β∗ΣZit+μi+τt+ϵit(1)