1. Medical Decision Making Although decision making is a prime activity of physicians, little time is spent on this subject in medical school curricula This lecture deals with the quantitative methods that can be used to aid physicians in decision making under uncertainty

2. Questions for the Decision Maker Efficacy and Effectiveness of Dx Tech Evaluation of outcomes of care not process New sources of information, written, www, other high tech Rational limits to memory Understandability of probability concepts by Pat and Phy. Understand uncertainty

7. Rationality Defined Based upon decision maker’s current assets Based upon possible consequences of choice When consequences uncertain, evaluated without violating basic rules of probability theory

10. Representativeness Difficulties Prior probability not taken into account Insensitivity to sample size Misconstruing randomness Not taking disconfirmatory evidence into account Misconstruing regression to the mean

11. Imagine you have the following scenario 1. If program A is adopted, 200 people will be saved 2. If program B is adopted, there is a 1/3 probability that 600 people will be saved and a 2/3 probability that no people will be saved

12. Now compare the following 1. If program C is adopted, 400 people will die 2. If program D is adopted, there is a 1/3 probability that no one will die and a 2/3 probability that 600 people will die

14. Availability When data are recent, familiar or salient they are more easily retrieved from memory and therefore seem more real than naturalistic frequencies

15. Anchoring and Adjusting Original estimates of probability biased because of availability and representativeness heuristics When asked to adjust estimates based upon new information unlikely to apply correct amount

16. Correct Use of Representativeness Evaluate how good are the cues Are they independent What is their prior probability Is the sample large enough Evaluate whether the results may be only regression to the mean

20. Sample Problem Mrs. Hull 56 year old,white female,160#,5’7” tall Smokes 1.5 pack cigarettes daily Increasing frequent episodes of typical angina, relieved by nitroglycerine Complete physical exam normal Special studies performed

21. Mrs. Hull (cont1) Coronary angiography shows 2 vessel disease Question of therapy and outcomes Medical vs. surgical therapy

26. Mrs. Hull (cont2) Perioperative mortality 2.5% Three year mortality 4.8% after surgery and 7.2% after medical therapy Probabilities of 3 levels of symptoms and death as outcomes

27. Mrs. Hull Outcomes