▁probability ▁of ▁each ▁answer . ▁Also ▁contrib uting ▁are ▁the ▁rules ▁of ▁combination ▁that ▁reflect ▁general ▁assumptions ▁about ▁the ▁data . ▁ ▁In ▁this ▁formal ism ▁a ▁degree ▁of ▁belief ▁( also ▁referred ▁to ▁as ▁a ▁mass ) ▁is ▁represented ▁as ▁a ▁belief ▁function ▁rather ▁than ▁a ▁Bay esian ▁probability ▁distribution . ▁Pro b ability ▁values ▁are ▁assigned ▁to ▁sets ▁of ▁possibilities ▁rather ▁than ▁single ▁events : ▁their ▁appeal ▁rest s ▁on ▁the ▁fact ▁they ▁naturally ▁encode ▁evidence ▁in ▁favor ▁of ▁propos itions . ▁ ▁D emp ster – S ha fer ▁theory ▁assign s ▁its ▁masses ▁to ▁all ▁of ▁the ▁subsets ▁of ▁the ▁propos itions ▁that ▁compose ▁a ▁system — in ▁set - the or etic ▁terms , ▁the ▁power ▁set ▁of ▁the ▁propos itions . ▁For ▁instance , ▁assume ▁a ▁situation ▁where ▁there ▁are ▁two ▁related ▁questions , ▁or ▁propos itions , ▁in ▁a ▁system . ▁In ▁this ▁system , ▁any ▁belief ▁function ▁assign s ▁mass ▁to ▁the ▁first ▁proposition , ▁the ▁second , ▁both ▁or ▁neither . ▁ ▁Bel ief ▁and ▁pla us ibility ▁Sh a fer ' s ▁formal ism ▁starts ▁from ▁a ▁set ▁of ▁possibilities ▁under ▁consideration , ▁for ▁instance ▁numerical ▁values ▁of ▁a ▁variable , ▁or ▁pairs ▁of ▁lingu istic ▁variables ▁like ▁" date ▁and ▁place ▁of ▁origin ▁of ▁a ▁re lic " ▁( ask ing ▁whether ▁it ▁is ▁ant ique ▁or ▁a ▁recent ▁fake ). ▁A ▁hypothesis ▁is ▁represented ▁by ▁a ▁subset ▁of ▁this ▁frame ▁of ▁disc ern ment , ▁like ▁"( M ing ▁dynast y