The test comes back and says the patient is sick what

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Unformatted text preview: ber of goodies. The test comes back and says the patient is “sick.” What is the probability the patient has the disease? probability P(D|“Sick”) = P(“Sick”|D)*P(D) / “Sick”) P(“Sick”) P( P(D|“Sick”) = P(“Sick”|D)*P(D) / P(“Sick”|D)*P(D)+P(“Sick”|ND)*PND) P(D|“Sick”) = P(“Sick”|D)*P(D) / P(“Sick”|D)*P(D) + P(“Sick”|ND)*PND) P(D|”Sick”) = (.69*.2) / (.69*.2 + .31*.8) ”Sick”) = .36 .36 Suppose the doctor gets the number of goodies back and makes the decision himself about whether the patient is healthy or sick. To represent the doctor’s decision or ’s we need Signal Detection Theory. SDT has two parameters: two d´ = d prime (the ability to distinguish d´ Healthy people from Sick people with the blood test) (Mean(s)-Mean(h)) / St Dev (h) blood β = beta or the response threshold (the doctor’s tendency to call a patient “Healthy” doctor’s or “Sick”) or 0.45 d’ 0.4 Healthy Sick 0.3 0.25 0.2 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 0.45 “Healthy” “Sick” d’ 0.4 Healthy Sick 0.3 0.25 0.2 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 Decision “Healthy” “Sick” State of the World Healthy Sick P(“H”|H) P(“S”|H) P(“H”|S) P(“S”|S) Each outcome has a name. E...
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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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