  Quite unexpectedly, kinetic theory is found to specify the correct definition
of average value to be employed in nonextensive statistical mechanics. It is
shown that the normal average is consistent with the generalized
Stosszahlansatz (i.e., molecular chaos hypothesis) and the associated
H-theorem, whereas the q-average widely used in the relevant literature is not.
In the course of the analysis, the distributions with finite cut-off factors
are rigorously treated. Accordingly, the formulation of nonextensive
statistical mechanics is amended based on the normal average. In addition, the
Shore-Johnson theorem, which supports the use of the q-average, is carefully
reexamined, and it is found that one of the axioms may not be appropriate for
systems to be treated within the framework of nonextensive statistical
mechanics.
