Probit Estimation output

[ak683]

Hi,

A (partial) copy of my probit estimation output is provided below. Take note that there is a warning and more importantly the fact that I get NA's for std errors/z-stats. kindly advise.

Dependent Variable: TIJ
Method: ML - Binary Probit (Quadratic hill climbing)
Date: 05/19/10 Time: 15:55
Sample (adjusted): 1 24940
Included observations: 18201 after adjustments
Convergence achieved after 28 iterations
WARNING: Singular covariance - coefficients are not unique
Covariance matrix computed using second derivatives

Coefficient Std. Error z-Statistic Prob.

C 8.436190 NA NA NA
BORDER -0.103809 NA NA NA
COM_LANG 0.544608 NA NA NA
LOG(DIJ) -0.981580 NA NA NA
LOG(LEXP) -6.853919 NA NA NA
EXPCODE=117100 -7.072969 NA NA NA
EXPCODE=130120 -12.43839 NA NA NA
EXPCODE=135040 -10.51805 NA NA NA
EXPCODE=137360 -11.77775 NA NA NA
EXPCODE=137880 -10.26672 NA NA NA
EXPCODE=138180 -9.938560 NA NA NA
EXPCODE=141200 -12.02376 NA NA NA

Regards,

Adeem

[startz]

Perhaps you've fallen into the dummy variable trap?