Download File - Eric Chavez MD MMI

Eric Chavez
Med Inf 406
Session 3 Decision Tree Assignment
Eric Chavez
Med Inf 406
Session 3 Decision Tree Assignment
Patient presents with symptoms. The decision point is to treat with the drug or do not treat with drug.
If you treat with the drug there is a 0.5 probability of hearing loss. If you have hearing loss there is a 0.3 probability of getting the
disease with the drug and a 0.7 probability of not getting the disease with the drug. If you get the disease there is 0.8 probability of blindness
and 0.2 probability of no blindness. The utility of taking the drug, getting hearing loss and getting blindness is 0.1. The utility of taking the drug,
getting hearing loss, and not getting blindness is 0.6. The utility of taking the drug, getting hearing loss, and not getting disease (and no
blindness) is 0.6.
If you treat with the drug there is a 0.5 probability of not getting hearing loss there is a 0.3 probability of getting the disease. You
still have a 0.3 probability of getting the disease and 0.7 probability of not getting the disease. If you get the disease there is 0.8 probability of
blindness and 0.2 probability of no blindness. The utility of taking the drug, not getting hearing loss, and getting blindness is 0.3. The utility of
taking the drug, not getting hearing loss, not getting disease, and not getting blindness is 1.0. The utility of taking the drug, not getting hearing
loss, and not getting disease is 1.0.
If you do not treat with the drug there is a 0.75 probability of getting the disease. If you get the disease there is 0.8 probability of
getting blindness and 0.2 probability of not getting blindness. The utility of not taking the drug, getting disease, and getting blindness is 0.3. The
utility of not taking the drug, getting the disease, and not getting blindness is 1.0.
If you do not treat with the drug there is a 0.25 probability of not getting the disease. The utility of not taking the drug and not
getting the disease (and not getting blindness) is 1.0.
Working from right to left we calculate the value for each of the branches. This is done by taking the utility at the end of each
branch and multiplying it by the probability of that branch. The values at the two ends of a node are then summed. These summed values make
up the utility of the branch further to the left. Then this utility number is multiplied by the probability at that branch. This process is repeated
further and further to the right until we arrive at the value of each branch off the decision point.
For this decision tree the value of treating with the drug is 0.656 which is larger than the value of not treating with the drug which
is 0.58. Therefore the decision should be to treat with the drug.