Hi all,

Just wondering as to why the sample sizes are different when I run Logit/probit and PMLE regression? I am running the model on the same sample, i.e. there are no missing values in my data for all the covariate I use, however, the sample sizes are still different between the two models.

I use the follwoing commanf:

firthlogit c $reg2
estimates store pmle1 ** sample size or number of obs 7081

logit c $reg2 , r
estimates store l1 ** sample size or number of obs 6903

probit c $reg2 ,r
estimates store p1 ** sample size or number of obs 6903

After I run the logit and probit I get the following message


"note: 9.income_week != 0 predicts failure perfectly
9.income_week dropped and 117 obs not used

note: 1.educ != 0 predicts failure perfectly
1.educ dropped and 61 obs not used"

Is there some way I can avoid these observations to not be dropped?

Thanks for the help !!


Kind Regards,
Aarushi