Psychological/Decision
Boy or Girl Paradox
A family has two children, one is a boy. What's the probability the other is a boy?
Overview
A probability puzzle showing how conditional probability can be counterintuitive.
A family has two children, and at least one is a boy. What's the probability both are boys? Intuition says 1/2, but the correct answer is 1/3. The three equally likely possibilities are: {older boy, younger boy}, {older boy, younger girl}, {older girl, younger boy}. Only one has two boys.