Here is another series of puzzles where more knowledge of the situation changes the odds, and even more knowledge changes the odds yet again.
1. There is a couple with exactly two children. What are the odds that both are girls?
2. The same as #1, but now you are told that one child is a girl. What are the odds that both are girls?
3. The same as #2, but now you are told that one child is a girl named Idhitri. What are the odds that both are girls?
For ease of calculation, assume the boy:girl ratio is 50:50 in the population.
I found these puzzles discussed in a very enjoyable book titled “Drunkard’s Walk” by Leonard Mlodinow. But I must warn you, discussing #3 with other people generates a lot of heat, just like what happened with the Monty Hall problem (http://www.marilynvossavant.com/articles/gameshow.html). Even after accepting the correct answer intellectually, it is not intuitively obvious.
Filed under: puzzle | Tagged: bayes theorem, Leonard Mlodinow, puzzle |
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