Conditional Probability in Two-Way Tables

Conditional Probability in Two-Way Tables

Investigate conditional probabilities and the relationships between events as the contents of a jar change.


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Putting It All Together

Answer these open ended questions on your own or with others to form deeper math connections.

Open-ended question 1

Place 6 spotted and striped balls in the jar along with 5 spotted balls that are not striped. Calculate P(A|B), the probability that a randomly selected ball is spotted, given that you know it is striped. Can you explain the results?

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Open-ended question 2

Place 3 spotted balls that are not striped in the container with 5 balls that are neither spotted nor striped. Why is P(A|B) undefined in this case? In general, what condition must exist if P(A|B) is undefined? Can P(B|A) be undefined? If so, under what conditions?

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Open-ended question 3

Fill the container with a random assortment of balls, including at least one ball of each type, and evaluate P(A|B), the probability that a randomly selected ball is spotted, given that you know it is striped. Can you explain why P(A|B) is equal to P(A and B)/P(B)? Will this relationship always hold? If not, what are the exceptions?

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Open-ended question 4

Under what conditions is P(A|B) equal to P(B|A)?

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