Thanks a lot, Now, I am facing a problem, the problem is just like the title said.
I want to conduct a reaserch the impact of education(1- primmary school; 2 - middle school; 3 - high school.. and so on) toward the people's number of reading books per year(0, ,1 , ..., ), but when I want to use the IV regression as the robust, The problem is I can't find the suitable command to fit these kind of data, I am confused about that, Coud you give me some advices?