35-probability&decisions

Normavetheory expectedulity fromreasoningtodecisions

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Unformatted text preview: reasoningtodecisions Expectedvalue E = P(x i )U(x i ) Fromreasoningtodecisions Expectedvalue E = P(x i )U(x i ) = Probability Value Thesetwoquan++esare enoughtocomputeop#mal decisions! Buthowgoodareweat es+ma+ngthem? MontyHallproblem A B C Thereisacarbehindonedoorandgoats behindtheotherdoors MontyHallproblem A B C Youpickadoor MontyHallproblem A B Youpickadoor Iopenadoor DoyouswitchtoBors+ckwithA? MontyHallproblem A 87%stay (Granberg&Brown,1995) B Bestanswer istoswitch DoyouswitchtoBors+ckwithA? MontyHallproblem MontyHallproblem Switchorstay? MontyHallproblem Tootrickywithouttraininginprobability? MarilynvosSavantpublishedthepuzzleinher ParadeMagazinecolumnin1991withthecorrect solu+on Le^ersfrommathprofessors "Ourmathdepartmenthadagoodself righteouslaughatyourexpense." "Youblewit!" "Howmanyiratemathema+ciansareneededto getyoutochangeyourmind?" (NewYorkTimes,1991) Medicaldiagnosis Adiseaseaffects1/1000people Thereisatestforthedisease Ifyouhavethedisease,testis100%posi+ve Ifyoudon'thavethedisease,testis95%nega+ve Arandompersontestsposi+ve Howlikelyisitthattheyhavethedisease? 5% 20% 50% 80% 95% (Casscellsetal.,1978) Medica...
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This note was uploaded on 04/29/2010 for the course PSYCH 85 211 taught by Professor Theissen during the Spring '10 term at Carnegie Mellon.

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