Martin Florig and Stephen J. Summers On the Statistical Independence of Algebras of Observables (51K, AMSTeX) ABSTRACT. We re-examine various notions of statistical independence presently in use in algebraic quantum theory, establishing alternative characterizations for such independence, some of which are also valid without assuming that the observable algebras mutually commute. In addition, in the context which holds in concrete applications to quantum theory, the equivalence of three major notions of statistical independence is proven.