Conditional Probability: The Two-Child Problem
Context and Assumptions
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Each child is independently a boy or a girl with probability 1/2.
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Birth order matters (older, younger), and twins/other complexities are ignored.
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The statement "at least one is a boy" provides only that constraint and does not bias which families are reported beyond ruling out two-girl families.
Question
A family has two children. You learn that at least one of them is a boy. What is the probability that both children are boys? Explain your reasoning.
Hint
List equally likely ordered pairs: BB, BG, GB, GG; remove combinations inconsistent with the condition.