My data has N<T, I know that DPD estimator is essentially efficient/unbiased for N>T. But in an attempt to replicate a similar study I prefer to use it.
Total panel obs : 231
I used DPD estimator and model ran fairly well.
Number of Coefficients estimated 3.
J-stat : 4.456718
Instrument rank : 7 with p_value 0,26 where Sargan test null is not rejected and I'm happy.
But my instructor commented that the degrees of freedom in Sargan chi square test (7-4 =3) is low and poses a problem.
But does not point out what is the problem. I couldnt find a clue in books, forums as to whether there is a problem or not.
Since I am aiming to finalize the project would very much appreciate your assistance. many thanks in advance.