Hausman检验
quietly xtreg y x1 x2,re
estimates store re
quietly xtreg y x1 x2,fe
estimates store fe
hausman fe re, sigmamore


y=a+b1* x1+b2* x2
DWH Test
reg x1 iv x2
predict r,e
reg y x1 r x2

只是为了发帖而发帖。。。。