  We clarify regions where the canonical approach works well at the finite
temperature and density in the Nambu-Jona-Lasinio (NJL) and Polyakov-NJL (PNJL)
models. The canonical approach is a useful method for avoiding the sign problem
in lattice QCD simulations at finite density, but it involves some parameters.
We find that number densities computed from the canonical approach are
consistent with exact values in most of the confinement phase within the
parameters, which are applicable in lattice QCD.
