Panel data is used when the data is varying across time and cross section, within which when your panel data has years per cross section more than 20. Then the data becomes long panel data thus simple OLS (FE / RE ) may not work. This tutorial provides the illustration of how to install xtpmg module and how to estimate three variants of panel ARDL model which are pooled mean group (PMG), mean group (MG) and dynamic Fixed effect (DFE). And later on compared the PMG and MG model using hausman test.