From this discussion, one way of conducting the subsample test is changing the equation from
Dependent_variables= pt + Independent_variables + fixed effects + error term
Dependent_variables= pt + developed_dummy * pt + Independent_variables + fixed effects + error term
while developed_dummy equal to 1 if the firm in developed countries and 0 otherwise I am wondering whether it is the case?
And if it is the case, how come we explain the meaning of the coefficient of developed_dummy*pt ?