  Widely studied quasiparticle models for quark gluon plasma is revisited here
to understand the statistical mechanics and thermodynamics of the system. We
investigate the statistical mechanics and thermodynamics inconsistencies
involved in these models and their consequences in the observables.
Quasiparticle model is a phenomenological model with few parameters and by
adjusting them all models fit the results of lattice gauge simulation of gluon
plasma \cite{bo.1}. However, after fixing 2 of the 3 parameters of the model by
physical arguments, only one quasiparticle model, which is consistent with both
statistical mechanics and thermodynamics, fits the Bielefeld lattice data
\cite{bo.1}. The same model also fits the recent lattice results of
Wuppertal-Budapest group \cite{fo.1}, which deals with precision SU(3)
thermodynamics for a large temperature range, reasonably well.
