396.The Added Baby
★★★conditional probabilityCh. 2 — Axiomatic and Conditional Probability444+ Problems in Probability
A room has 5 babies: 2 boys and 3 girls. A baby of unknown sex (boy or girl with equal probability) is added. One of the 6 babies is then selected at random, and it is a boy. What is the probability that the added baby is a boy?
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The evidence "a random pick was a boy" is more likely in the world where the added baby is a boy — quantify with Bayes.
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