For suppose the doctor wants to maximize the expected

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Unformatted text preview: ptimal place for the doctor to put his response threshold (β)? threshold SDT tells the decision maker where SDT to locate the response threshold for a given objective. for Suppose the doctor wants to maximize the expected value of his decision. the Decision “Healthy” “Sick” State of the World Healthy v(CR) Sick v(M) v(FA) v(H) He can assign a value to each of the four He possible outcomes. possible β is the ratio of the height of the distributions of sick people and healthy people at any value of g, the # of goodies in the blood. value β = p(g|S)/p(g|H) The optimal place to set β is where it = The p(H)/p(S) * [v(CR) + v(FA)]/[v(H) + v(M)] Suppose p(H) = .8 and p(S) = .2 Suppose Decision “Healthy” “Sick” State of the World Healthy 200 ­50 Sick ­200 800 β =p(H)/p(S) * [v(CR) + v(FA)]/[v(H) + v(M)] v(M)] = .8/.2 *(200 + -50)/(800 + -200) = .8*.2 * 150/600 = 4/1 * 1/4 =1 0.45 “Healthy” 0.4 “Sick” 0.3 0.25 0.2 Healthy Sick 0.15 0.1 0.05 # Goodies in the Blood 14 5 13 0 12 5 12 0 11 5 10 0 85 70 0 55 Probability of Disease 0.35 The optimal location for the response threshold depends on the costs and benefits of decisions and the base rate for the disease. for Suppose the doctor wants to maximize the probability of a correct decision. the Decision “Healthy” “Sick” State of the World Healthy v(CR) Sick v(M) v(FA) v(H) Suppose p(H) = .8 and p(S) = .2 Suppose Decision “Healthy...
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This document was uploaded on 02/15/2014 for the course PSYCH 002 at Community College of Philadelphia.

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