Events Influencing Each Other Conditional Probability Bayes’ Theorem Definition. For events A and B with P ( B ) > 0 , the conditional probability of A given that B has occurred is P ( A | B ) : = P ( A ∩ B ) . P ( B ) S A B � � � � � � � � � � � � � � � � � � logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Definition. For events A and B with P ( B ) > 0 , the conditional probability of A given that B has occurred is P ( A | B ) : = P ( A ∩ B ) . P ( B ) S A B � � � � � � � � � � � � � � � � � � A ∩ B logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Definition. For events A and B with P ( B ) > 0 , the conditional probability of A given that B has occurred is P ( A | B ) : = P ( A ∩ B ) . P ( B ) S A B � � � � � � � � � � � � � � � � � � A ∩ B logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Definition. For events A and B with P ( B ) > 0 , the conditional probability of A given that B has occurred is P ( A | B ) : = P ( A ∩ B ) . P ( B ) S A B B � � � � � � � � � � � � � � � � � � A ∩ B logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Definition. For events A and B with P ( B ) > 0 , the conditional probability of A given that B has occurred is P ( A | B ) : = P ( A ∩ B ) . P ( B ) S A B B � � � � � � � � � � � � � � � � � � A ∩ B logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Definition. For events A and B with P ( B ) > 0 , the conditional probability of A given that B has occurred is P ( A | B ) : = P ( A ∩ B ) . P ( B ) S A B B � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � A ∩ B logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Definition. For events A and B with P ( B ) > 0 , the conditional probability of A given that B has occurred is P ( A | B ) : = P ( A ∩ B ) . P ( B ) S A B B � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � A ∩ B A ∩ B logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Definition. For events A and B with P ( B ) > 0 , the conditional probability of A given that B has occurred is P ( A | B ) : = P ( A ∩ B ) . P ( B ) S A B B � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � A ∩ B A ∩ B For P ( A | B ) , the set B becomes the sample space. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” P ( B ) = 4 52 = 1 13 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” P ( B ) = 4 52 = 1 13, P ( A ∩ B ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 13, P ( A ∩ B ) = 52 · 51 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 P ( A | B ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 P ( A | B ) = P ( A ∩ B ) P ( B ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) 13 · 17 = 1 P ( B ) 13 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 P ( B ′ ) = 48 52 = 12 13 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 P ( B ′ ) = 48 52 = 12 13, P ( A ∩ B ′ ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 52 · 51 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 16 52 · 51 = 13 · 17 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 16 52 · 51 = 13 · 17 P ( A | B ′ ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 16 52 · 51 = 13 · 17 P ( A | B ′ ) = P ( A ∩ B ′ ) P ( B ′ ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 16 52 · 51 = 13 · 17 P ( A | B ′ ) = P ( A ∩ B ′ ) 16 13 · 17 = P ( B ′ ) 12 13 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 16 52 · 51 = 13 · 17 P ( A | B ′ ) = P ( A ∩ B ′ ) 16 = 4 13 · 17 = P ( B ′ ) 12 51 13 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 16 52 · 51 = 13 · 17 P ( A | B ′ ) = P ( A ∩ B ′ ) 16 = 4 13 · 17 = P ( B ′ ) 12 51 13 Proposition. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 16 52 · 51 = 13 · 17 P ( A | B ′ ) = P ( A ∩ B ′ ) 16 = 4 13 · 17 = P ( B ′ ) 12 51 13 Proposition. Multiplication rule: P ( A ∩ B ) = P ( A | B ) · P ( B ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A = “the second card drawn from a deck is a queen” B = “the first card drawn from a deck is a queen” 4 · 3 P ( B ) = 4 52 = 1 1 13, P ( A ∩ B ) = 52 · 51 = 13 · 17 1 P ( A | B ) = P ( A ∩ B ) = 1 13 · 17 = 1 P ( B ) 17 13 13, P ( A ∩ B ′ ) = 48 · 4 P ( B ′ ) = 48 52 = 12 16 52 · 51 = 13 · 17 P ( A | B ′ ) = P ( A ∩ B ′ ) 16 = 4 13 · 17 = P ( B ′ ) 12 51 13 Proposition. Multiplication rule: P ( A ∩ B ) = P ( A | B ) · P ( B ) (Can be used to double check and to compute probabilities of intersections.) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 . logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 . P ( A 1 ∩ A 2 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 . P ( A 1 ∩ A 2 ) = P ( A 1 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 . P ( A 1 ∩ A 2 ) = P ( A 1 ) P ( A 2 | A 1 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 . P ( A 1 ∩ A 2 ) = P ( A 1 ) P ( A 2 | A 1 ) 2 = 3 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 . P ( A 1 ∩ A 2 ) = P ( A 1 ) P ( A 2 | A 1 ) 2 3 · 1 = 2 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Three cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all three cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 . P ( A 1 ∩ A 2 ) = P ( A 1 ) P ( A 2 | A 1 ) 2 3 · 1 = 2 1 = 3 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . P ( A 1 ∩ A 2 ∩ A 3 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . P ( A 1 ∩ A 2 ∩ A 3 ) = P ( A 3 | A 1 ∩ A 2 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . P ( A 1 ∩ A 2 ∩ A 3 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 1 ∩ A 2 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . P ( A 1 ∩ A 2 ∩ A 3 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 1 ∩ A 2 ) = P ( A 3 | A 1 ∩ A 2 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . P ( A 1 ∩ A 2 ∩ A 3 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 1 ∩ A 2 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 2 | A 1 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . P ( A 1 ∩ A 2 ∩ A 3 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 1 ∩ A 2 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 2 | A 1 ) P ( A 1 ) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . P ( A 1 ∩ A 2 ∩ A 3 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 1 ∩ A 2 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 2 | A 1 ) P ( A 1 ) 1 2 · 2 3 · 3 = 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. Four cards are placed face down on a table. One of them is the queen of hearts. What is the probability that all four cards must be turned over to find the queen of hearts? A 1 : = first card not the queen of hearts. A 2 : = second card not the queen of hearts. A 3 : = third card not the queen of hearts. The event we are interested in is A 1 ∩ A 2 ∩ A 3 . P ( A 1 ∩ A 2 ∩ A 3 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 1 ∩ A 2 ) = P ( A 3 | A 1 ∩ A 2 ) P ( A 2 | A 1 ) P ( A 1 ) 1 2 · 2 3 · 3 = 4 1 = 4 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40, P ( B | A 1 ) = 0 . 30. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40, P ( B | A 1 ) = 0 . 30. A 2 = purchased model 2. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40, P ( B | A 1 ) = 0 . 30. A 2 = purchased model 2. P ( A 2 ) = 0 . 35 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40, P ( B | A 1 ) = 0 . 30. A 2 = purchased model 2. P ( A 2 ) = 0 . 35, P ( B | A 2 ) = 0 . 05. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40, P ( B | A 1 ) = 0 . 30. A 2 = purchased model 2. P ( A 2 ) = 0 . 35, P ( B | A 2 ) = 0 . 05. A 3 = purchased model 3. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40, P ( B | A 1 ) = 0 . 30. A 2 = purchased model 2. P ( A 2 ) = 0 . 35, P ( B | A 2 ) = 0 . 05. A 3 = purchased model 3. P ( A 3 ) = 0 . 25 logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40, P ( B | A 1 ) = 0 . 30. A 2 = purchased model 2. P ( A 2 ) = 0 . 35, P ( B | A 2 ) = 0 . 05. A 3 = purchased model 3. P ( A 3 ) = 0 . 25, P ( B | A 3 ) = 0 . 15. logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
Events Influencing Each Other Conditional Probability Bayes’ Theorem Example. A car company sells three different models of compact cars. The probabilities that one of these models is selected (by a compact car buyer) are 0 . 40 , 0 . 35 and 0 . 25 , respectively. The probabilities that a buyer of any of these cars will buy the same model again are 0 . 30 , 0 . 05 and 0 . 15 , respectively. Given that a buyer has just purchased a compact car of the same model that was previously owned, what are the chances that the model was the first, second or third of the above models? Name the models 1, 2 and 3, respectively. B = purchased previously owned model again. A 1 = purchased model 1. P ( A 1 ) = 0 . 40, P ( B | A 1 ) = 0 . 30. A 2 = purchased model 2. P ( A 2 ) = 0 . 35, P ( B | A 2 ) = 0 . 05. A 3 = purchased model 3. P ( A 3 ) = 0 . 25, P ( B | A 3 ) = 0 . 15. What is P ( A i | B ) ? logo1 Bernd Schr¨ oder Louisiana Tech University, College of Engineering and Science Conditional Probability
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