For a sample of n=243, I ran the following logistic regression in STATA, with inv being a dummy variable equal to 1 if an individual will invest into a social corporation and zero if not. All other variables are independent variables for the attitude of individuals or financial motives.

logistic inv psa ecb pce pre pri age female degree urban imp_soc imp_eco imp_fin

In my sample of n=243 I know that 99 individuals have invested on the capital market before and I want to run the same regression only for these individuals. I am able to drop all other observations and run the regression, but is there another way to do it?

I also included a variable for this in my regression (investment experience), but didn't get significant results. So I decided to run the regression for the subgroup, which looks very interesting. If you are into statistics, is it ok to proceed like that?

Thanks a lot in advance.