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anonymous
 one year ago
HELP WITH PROBABILITY! Question posted below :)
anonymous
 one year ago
HELP WITH PROBABILITY! Question posted below :)

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anonymous
 one year ago
Best ResponseYou've already chosen the best response.0An art critic is surveying a gallery to find a piece that he would like to buy. The piece however has been copied by numerous people throughout the years such that 20% of the paintings in circulation are fake. the critic correctly identifies a fake as being fake 90% of the time; but only correctly identifies a real piece as being real half the time. The critic finds the painting and believes is is a fake. What is the probability that the painting is real? 40% 50% 69% 80%

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Hi ganeshie8, I've drawn a tree diagram of probabilities, but am having some trouble making sense of the question...

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.280% of available pieces are real and 20% are fake : dw:1437554345284:dw

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.2The probability for critic identifying "fake piece" as "fake" is 90% The probability for critic identifying "real piece" as "real" is 50% dw:1437554570150:dw

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Yep, thats what I did too

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.2fill in the probabilities on other braches dw:1437554742335:dw

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.2we're given that the critic identifies the piece as fake, so highlight those branches : dw:1437554822270:dw

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.2p("real"  "cfake") = P("real" and "cfake") / P("cfake")

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.2= 0.8*0.5 / (0.8*0.5 + 0.2*0.9)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0why do you divide those two?

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.2because we know that the critic identified the piece as fake, the sample space reduces to only those two branches that end with "cfake"

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0okay so out of all the times that he says its fake, we are looking at the times its actually real

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0Thanks so much for your help @ganeshie8 !!!!!!

ganeshie8
 one year ago
Best ResponseYou've already chosen the best response.2np you could work this using bayee's theorem formula but i feel tree diagrams are a great way to visualize/work these problems involving conditional probability

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0whats bayee's theorem? If its quick to explain that would be great, otherwise ill wikipedia it!
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