why are the zeros in a difference in differences test can an ols model use variable zeros why would ols estimate the difference in difference model why should ols models be run with zeros? why do the lls model contain zeroes? how does a model estimate differences in difference difference analysis model if dependent variable is zero why do firm level data have zeroes what is a normality assumption in the difference in differences model? why is there a difference in difference model what makes the difference in a model of investment what variable has zeros? how do you estimate a difference in differences model how do i predict a difference in a normality model average deviation difference what is the difference of the models dependent variable and normality assumption what is the difference in the model of a firm when a model of differences in differences has many zeros what variable is considered the independent variable? when a difference in differences model has lots of zeros how do you compute difference in differences