A man has two children. One of them is a boy.

[Diablo]

"A man has two children. One of them is a boy".
What is the probability that the other one is a boy?

If the statement is true the answer is no probability of the other child being a boy otherwise the statement is false

 

[nwgull]

To be honest, the first question is still 1 in 2. The only way it could be 1 in 3 is if the person posing the question deliberately looked for a man with a boy, and even then it depends on how the man was selected. And that's not a reasonable assumption from the question.

The only fair assumption it's possible to make is that the man was chosen randomly and that we were randomly chosen the gender of one of his children. And it's 1 in 2.

It is, without doubt, 1 in 2.

The mathematical model showing 1 in 3 is wrong in that it ignores the fact that 2 of the potential 4 scenarios - GG, BG, GB and BB - are discounted by the fact that a man with a boy can't have 2 girls and he has to have had either the boy first or the boy second - he can't have both.

 

[AlbionPics&SouthCoastTwit]

Currently 17 pages of ambiguity.