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Unformatted text preview: EE 178 Handout #2 Probabilistic Systems Analysis January 17, 2008 Homework #2 Due Thursday, January 24, 2008 1. Catching the train. The probability that Riddley Walker goes for a run in the morning before work is 2 / 5. If he runs then the probability that he catches the train to work is 2 / 5. If he does not run then the probability that he catches the train to work is 1 / 2. If he does not catch the train, then he catches the bus. The model holds Monday through Friday. a. Draw a tree showing the probabilities governing Riddley’s morning. b. What is the probability that Riddley catches the train any morning? c. You are told that Riddley made the train — what is the probability that he ran? 2. Testing for a disease. The probability that a man has a particular disease is 1 / 20. John is tested for the disease but the test is not totally accurate. The probability that a person with the disease tests negative is 1 / 50 while the probability that a person who does not have the disease tests positive is 1 / 10. John’s test returns positive. a. Find the probability that John has the disease. b. You are now told that this disease is hereditary. The probability that a son suffers from the disease if his father does is 4 / 5, the probability that a son is infected with the disease even though his father is not is 1 / 95. What is the probability that Steve95....
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- Spring '08
- Probability, Dice, Fischer, Riddley Walker