I have a panel data with variables ROE as y variable ,Debtratio as dependent variable,firm size and firm growth as control variables and a dummy variable(technology).My aim is to measure the effect of debt ratio on ROE controlling for firm size and firm growth for when the company is a high tech==1 and low tech==0.Running the fixed effect model omits the dummy variable technology because obviously it is time invariant over the course of 10 years for an entity.i would also measure the interaction between Debt ratio and technology on ROE.i have ran fe,re and be and all gave me different values for all measurements.My request is what is the correct thing to do in this situation?