Biomedical Informatics 4th Edition by Edward Shortliffe, James Cimino

Exercise 7

Calculate the following probabilities for a patient about to undergo CABG surgery (see Example 2) :
(a) The only possible, mutually exclusive outcomes of surgery are death, relief of symptoms (angina and dyspnea), and continuation of symptoms. The probability of death is 0.02, and the probability of relief of symptoms is 0.80. What is the probability that the patient will continue to have symptoms?
(b) Two known complications of heart surgery are stroke and heart attack, with probabilities of 0.02 and 0.05, respectively. The patient asks what chance he or she has of having both complications. Assume that the com plications are conditionally independent, and calculate your answer.
(c) The patient wants to know the probability that he or she will have a stroke given that he or she has a heart attack as a complication of the surgery. Assume that 1 in 500 patients has both complications, that the probability of heart attack is 0.05, and that the events are independent. Calculate your answer.