Dear Statalisters,

I am currently running some analysis on a few different dependent variables in a 2-period panel with a fixed effects estimator. I get good results for each dependent variables, however, I feel like I have an upward bias in my predictor.
I have strong literature backing supporting that 2 of my dependent variables should be positively prediced by the predictor, whereas 2 should be negative. What I get is that the 2 positive ones are positive with a high magnitude, the 2 that are meant to be negative are also positive with a really small magnitude. I strongly believe that my regression suffers from omitted variable bias.

I have constructed my panel from a survey with hundreds and hundreds of observation. I have consulted literature to find the appropriate control variables, but I still think I have an upward bias in there (as I am doing something slightly different than literature).

Is there any way to find out what causes this bias? Or what should I do in order to adress this?

Many thanks in advance,
Andreas