Probability of Truth Given Corroboration

Probability · Medium · Free problem
Alice and Bob are witnesses to a crime. When asked questions, Alice tells the truth with probability $p_A$ and lies with probability
- p_A$. Bob tells the truth with probability $p_B$ and lies with probability
- p_B$. Their truthfulness is independent. The detective asks Alice a yes/no question. She gives an answer, and Bob then states that Alice's answer is truthful. Given that $p_A = 1/3$ and $p_B = 3/5$, find the probability that Alice actually told the truth.

Open the full interactive solver, hints, and worked solution →