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Unformatted text preview: c Kendra Kilmer October 11, 2011 Section 7.5  Conditional Probability and Independent Events Example 1 : A survey is done of people making purchases at a gas station: buy drink ( D ) no drink ( D c ) Total buy gas ( G ) 20 15 35 no gas ( G c ) 10 5 15 Total 30 20 50 a) What is the probability that a person buys a drink? b) What is the probability that a person doesn’t buy a drink? c) What is the probability that a person buys gas and a drink? d) What is the probability that a person buys gas but not a drink? e) What is the probability that a person who buys a drink also buys gas? f) What is the probability that a person who doesn’t buy a drink buys gas? Definition : If E and F are events in an experiment and P ( E ) 6 = 0, then the conditional probability that the event F will occur given that the event E has already occurred is P ( F  E ) = P ( E ∩ F ) P ( E ) Definition : The Product Rule is found by rearranging the above formula as follows: P ( E ∩ F ) = P ( E ) · P ( F  E ) 11 c Kendra Kilmer October 11, 2011...
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 Fall '08
 JillZarestky
 Conditional Probability, Probability, Probability theory, Kendra Kilmer

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