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Take a random parent with two children. You ask them if at least one is a boy and they say yes. The probability that the other is a girl is 66.6% Take another
by WilliamLP 18y ago
Take a random parent with two children. You ask them if at least one is a boy and they say yes. The probability that the other is a girl is 66.6%
Take another random parent with two children. You ask them if the oldest child is a boy and they say yes. Now the probability that the other is a girl is 50%.
This confuses people. (The point is the second scenario gives you more information since it's a subset of the first.)
- thras 18y agoExactly correct. Your comment should be at the top of this discussion. It took me forever to figure the above out when I first ran into this puzzle in 7th grade. And although this problem is often used to show that humans are bad at doing probability in their heads, note how simple it is to do the probability calculation for the two scenarios that you've mentioned. What's actually hard for humans is describing models or simulations, not doing the probability. Once you explained the possibilities for original problem in a more detailed way, the answer(s) becomes obvious.