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.