Why can't you just disregard the existing boy and reframe the question as the probability that the other child is a boy, and the space of all possible answers is BG and BB, equally probable (1/2)? Not really following explanations I find online.

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joshuaissac 4 days ago | parent [-]

Because GB is also a possibility. You are not told that the existing boy is the elder child.

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jimmaswell 4 days ago | parent [-]

https://www.online-python.com/Q5leTWuvb6

https://www.online-python.com/RueVd2514m

No matter how I frame or interpret this question, the birthdays and birth order appear completely irrelevant - the results are still ~0.50 as expected. Whatever the author was trying to say, they didn't communicate it well. I'm really curious exactly what word or phrase the author thought I was supposed to take to mean something else. If someone could edit one of these simulations to show what the author intended then that would probably be the clearest way.

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LudwigNagasena 4 days ago | parent [-]

https://www.online-python.com/6LDtZz7lMh

* Take all families with two children

* Take a subset where at least one child is a boy born on Tuesday

* Take a subset of the previous subset where all children are boys

* The share of the 2nd subset relative to the 1st subset is around 48%

	▲	jimmaswell a day ago \| parent [-]
		Yeah, makes sense. I thought I saw someone say 1/3 which is what seemed impossible.