Suppose you have a friend with two children. He tells you that one is a boy born on a Friday

Suppose you have a friend with two children. He tells you that one is a boy born on a Friday.

What's the probability that both are boys?

Well, Veeky Forums?

75%

50%, we've been through this before

assuming no other information is available, roughly 50%.
I don't know if having one boy makes it more likely (genetically) to have another one or something like this, but I doubt it.

This.

Inb4: Frequentist vs. Bayesian debate

100%

What does this have to do with Frequents vs Bayesians?

50%
I'm not meming. Assuming boys and girls are equally likely to be born, it is 50% you dumb frogposter

Given the fact that the name Friday comes from the Old English Frīġedæġ, meaning the "day of Frige", and Frige was a goddess, the chance that an another boy is born on a Firday is pretty low. Say 25% or less.

1/3
Possibilities are
BG
GB
BB

just look up his facebook

But you already know, that the first one is not a girl. Therefore the possibilities are only
BB
BG
Therefore 50%.

>ITT: brainlets

4 possibilities

BB
BG
GB
GG

We know that at least one is a boy, meaning there are 3 possibilities.

BB
BG
GB

Of these, only one is both boys, and so the probability is .33

Wait, no, I'm fucking retarded, the probability is .50

Why is Veeky Forums so ignorant when it comes to probability? It's by far the subject most people get wrong around here. Maybe it's a big ruse and you guys just pretend to be retarded?

[math]\textbf{Bayes' theorem}[/math]

P(2B|1B) = P(1B|2B) * P(2B) / P(1B)

P(2B|1B) = 1 * 0.5^2 / (1-0.5^2)

P(2B|1B) = 0.25 / 0.75

P(2B|1B) = 0.333

Why are you ignoring the information that he was born on a Friday?

50/50 because their births are independent of each other and there is roughly a 50/50% chance of a child being male when concieved

>Why are you ignoring the information that he was born on a Friday?

Because this does not give you any useful information. If we knew whether he was born first or second would change the answer. The fact that he was born on a Friday adds nothing to the analysis.

It's 50%.

1 x 1/2 = .5

7

Did you try doing the analysis with the extra information?

(There are 14 possibilities for each child: Boy/Monday, ..., Boy/Sunday, Girl/Monday, ...,Girl/Sunday. If you do a similar analysis to your previous post you get a different answer)

He never said the first was a boy, though, only that one was a boy.

biologically, 50%.
not considering mutations that can make the baby born with both genitals.

Take your pedophile cartoons back to .