▁in ▁their ▁estimate ▁by ▁more ▁than ▁$ 4 0 , ▁they ▁may ▁find ▁themselves ▁on ▁the ▁street , ▁while ▁if ▁they ▁er red ▁by ▁more ▁than ▁$ 5 0 , ▁they ▁may ▁find ▁themselves ▁d ining ▁in ▁op ul ence . ▁ ▁As ▁stated , ▁this ▁example ▁is ▁only ▁descript ive , ▁and ▁does ▁not ▁enable ▁any ▁decision ▁making ▁– ▁in ▁applications , ▁one ▁cons iders ▁alternative ▁decision ▁rules , ▁and ▁often ▁situations ▁with ▁more ▁complex ▁uncertainty . ▁ ▁Consider ▁now ▁the ▁worker ▁thinking ▁of ▁moving ▁to ▁a ▁different ▁town , ▁where ▁the ▁work ▁pays ▁less ▁but ▁lod g ings ▁are ▁che aper . ▁Say ▁that ▁here ▁they ▁estimate ▁that ▁they ▁will ▁ear n ▁$ 8 0 ▁per ▁week , ▁but ▁lod ging ▁only ▁costs ▁$ 4 4 , ▁while ▁entertain ment ▁still ▁costs ▁$ 1 5 0 . ▁In ▁that ▁case ▁the ▁robust ness ▁function ▁will ▁be ▁$ 3 6 , ▁while ▁the ▁opportun eness ▁function ▁will ▁be ▁$ 7 0 . ▁If ▁they ▁make ▁the ▁same ▁errors ▁in ▁both ▁cases , ▁the ▁second ▁case ▁( mov ing ) ▁is ▁both ▁less ▁robust ▁and ▁less ▁opport une . ▁ ▁On ▁the ▁other ▁hand , ▁if ▁one ▁measures ▁uncertainty ▁by ▁relative ▁error , ▁using ▁the ▁fraction al ▁error ▁model : ▁ ▁in ▁the ▁first ▁case ▁robust ness ▁is ▁ 4 0 % ▁and ▁opportun eness ▁is ▁ 5 0 %, ▁while ▁in ▁the ▁second ▁case ▁robust ness ▁is ▁ 4 5 % ▁and ▁opportun eness ▁is ▁ 8 7 . 5 %, ▁so