Hello.
I am trying to show that the Sargan statistics of a classical linear 2SLS estimation can be expressed as the form nR^2, assuming homoscedasticity.
I start with the original form of Sargan statistics:
S=N x (e’Pz e)/(e’e)
Where n is the sample size, Pz= Z(Z’Z)^-1Z’ and Z is the nxL...