  The factorization problem of $q$-exponential distribution within nonextensive
statistical mechanics is discussed on the basis of Abe's general
pseudoadditivity for equilibrium systems. it is argued that the factorization
of compound probability into product of the probabilities of subsystems is
nothing but the consequence of existence of thermodynamic equilibrium in the
interacting systems having Tsallis entropy. So the factorization does not needs
independent noninteracting systems and should be respected in all exact
calculations concerning interacting nonextensive subsystems. This consideration
makes it legitimate to use $q$-exponential distribution either for composite
system or for single body in many-body systems. Some known results of ideal
gases obtained with additive energy are reviewed.
