The difference between did model and fixed effect model

The main difference between them lies in the way and goal of data processing.

DID model, also known as double-difference model, is mainly used to evaluate the effect of policies or treatments. It estimates the therapeutic effect by comparing the time changes between the treatment group and the control group.

The fixed effect model is a more general panel data model, which eliminates the possible missing variable bias by controlling the individual characteristics that do not change with time.