Hi,

I have done Poisson ML and NB2 estimation.

Cameron and Trivedi 2010 says that the estimation should be similar (NB2 estimation should be around 15% of Poisson ML).

However, my Poisson ML and NB2 estimation give opposite estimation. One says the main variable of interest increases and the other says decreases.

Would someone be able to tell me what could possibly be going wrong?

Many thanks,


N