In this work, a quantitative analysis of reported metallic and insulating behaviour of resistivity in perovskite manganites La0.8Sr0.2MnO3 is established. An effective inter-ionic interaction potential (EIolP) with the long-range Coulomb, van der Waals (vdW) interaction and short-range repulsive interaction up to second-neighbour ions within the Hafemeister and Flygare approach was employed to estimate the Debye and Einstein temperature and was found to be consistent with the available experimental data. The electrical resistivity data in low temperature regime (T < T-MI) were theoretically analyzed within the framework of the classical electron-phonon model of resistivity, for example, the Bloch-Gruneisen (BC) model. The Bloch-Gruneisen (BC) model and terms T-2, T-4.5 simplify the electron-phonon, electron-electron and electron-magnon scattering processes. On the other hand, in high temperature regime (T > T-MI) the insulating nature is discussed with Mott's variable range hopping (VRH) model and small polaron conduction (SPC) model. For T > T-MI SPC model is more appropriate than the VRH model. The SPC model consistently retraces the higher temperature resistivity behaviour (T > theta(D)/2). The metallic and semiconducting resistivity behaviours of La0.8Sr0.2MnO3 manganites are analyzed, to the knowledge, for the first time highlighting the importance of electron-phonon, electron-electron, electron-magnon interactions and small polaron conduction. (C) 2011 Elsevier B.V. All rights reserved.