We reexamine various notions of statistical independence presently in
use in algebraic quantum theory, establishing alternative characteriza
tions for such independence, some of which are also valid without assu
ming that the observable algebras mutually commute. In addition, in th
e context which holds in concrete applications to quantum theory, the
equivalence of three major notions of statistical independence is prov
en. (C) 1997 American Institute of Physics.