easy   Probability

Under Oath I

A release-checked easy problem for training Conditional Probability.

Question

Alice and Bob are witnesses to a crime. When asked questions, Alice and Bob respectively tell the truth with probability $p_A$ and $p_B$ (and lie with respective probabilities $1-p_A$ and $1-p_B$). The detective asks Alice a question, she gives an answer, and Bob confirms the answer given by Alice is truthful. Find the probability that Alice told the truth when $p_A = 1/3$ and $p_B = 3/5$.

Practice focus

This Probability problem is tagged Conditional Probability. State the random variables and conditioning information explicitly, then check the result against boundary cases before opening hints or a solution.

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