Hi Ken, Thanks a lot for the reply! I will get started on these. I have couple of questions here In the two way fixed effect model, how would I calculate the total impact of coupons (we get 4 coefficients, three for lag terms and one for current coupon)? are the coefficients additive? (α1+α2+α3+α4) or should we use some decaying exponential form for the coefficients corresponding to the lags  How can I calculate the total impact (annual) of the program, from the regression model I would get the impact on average per subject for a period of 4 months, can I project it to 12 months?  Thanks! ... View more