Drug testing decision tree
Benefits Given probabilities
Identifying user 25 Prior probabilities
User
Costs 0.05
Test cost 1
Barring non-user 50 Conditional probabilities of test results
Not identifying user 20 User
Violation of privacy 2 Positive 0.93
Negative 0.07
Key probabilities
PrUser 0.05 Bayesian revision
PrFalseNegative 0.07 Joint probabilities
PrFalsePositive 0.03 User
Positive 0.047
Range names
Negative 0.004
BarNonUser: B8
IdentUser: B4
NotIdentUser: B9 Posterior probabilities
PrFalseNeg: B14 User
PrFalsePos: B15 Positive 0.620
PrUser: B13 Negative 0.004
TestCost: B7
ViolPrivacy: B10 Yes
62.0% #NAME?
25 #NAME?
7.5% User?
Positive
0 #NAME?
38.0% #NAME?
No
-52 #NAME?
#NAME? Test results
Yes
-1 #NAME?
0.4% #NAME?
Yes
-20 #NAME?
92.5% User?
Negative
0 #NAME?
99.6% #NAME?
No
-2 #NAME?
Test?
Drug testing
#NAME?
5.0% #NAME?
Yes
-20 #NAME?
#NAME? User?
No
0 #NAME?
95.0% #NAME?
No
0 #NAME?
Non-user
0.95
Non-user
0.03
0.97
Non-user Sums
0.029 0.075
0.922 0.925
Non-user
0.380
0.996