Suppose you have a friend with two children. He tells you that

50%, we've been through this before

>>8241508
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.

>>8241524
This.

Inb4: Frequentist vs. Bayesian debate

>>8241508
100%

>>8241533
What does this have to do with Frequents vs Bayesians?

>>8241508
50%
I'm not meming. Assuming boys and girls are equally likely to be born, it is 50% you dumb frogposter

>>8241508
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

>>8241508
just look up his facebook

>>8241610
But you already know, that the first one is not a girl. Therefore the possibilities are only
BB
BG
Therefore 50%.

>>8241508
>ITT: brainlets

>>8241508
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

>>8242127
Wait, no, I'm fucking retarded, the probability is .50

Why is /sci/ 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

>>8242150
Why are you ignoring the information that he was born on a Friday?

>>8241508
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

>>8242159
>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

>>8242515
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)

>>8241677
He never said the first was a boy, though, only that one was a boy.

File: AAI_Ema_Skye_Confident_2.gif (343KB, 256x192px) Image search: [Google]

343KB, 256x192px

>>8241508
biologically, 50%.
not considering mutations that can make the baby born with both genitals.