Every final decision, order, or regulation of the Commission is prima facie correct and shall be affirmed unless clearly shown to be:

            (1)      unconstitutional;

            (2)      outside the statutory authority or jurisdiction of the Commission;

            (3)      made on unlawful procedure;

            (4)      arbitrary or capricious;

            (5)      affected by other error of law; or

            (6)      if the subject of review is an order entered in a contested proceeding after a hearing, unsupported by substantial evidence on the record considered as a whole.