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

[StonehamPark]

Two coins:
One coin has already been flipped and has landed on heads (boy).
The probability that the second coin will land on heads is 1 in 2.

The answer to the ridiculous question is; there's a 1 in 2 chance the other child is a boy (or the second coin to be flipped lands on heads).

 

[Diablo]

No he did get one(fact). Then he got two more.

yes ...so if he had stopped at one for the weekend you would have been correct but he didn`t he scored three...I`d love you to be a bookie I`d bet on 0-0 every game... you would pay out because I`m correct part of the way through game..

 

[Triggaaar]

As per my reply above, I do NOT believe that is a premise / scenario you can take from the original question'. This was simply presented to us as fact, that (at least) one child was a boy.

But why were we told one was a boy, why weren't we told one was a girl? This is part of the facts, and you're overlooking it. But even if we can't take it from the original question, we can take it from subsequent questions we've posed, and you've still tried to argue that it's 1 in 3, and it's not.

You've been happy to go with my example of 4 families - you can do the same with the 100 families, or the whole population, and the answer is the same - 50%.


In our example of 4 families, on two occasions the couple come forward and say 'boy' and on two occasions the couple come forward and say 'girl'. It doesn't get simpler than that, I don't know what more you want.

 

[Triggaaar]

yes ...so if he had stopped at one for the weekend you would have been correct but he didn`t he scored three...I`d love you to be a bookie I`d bet on 0-0 every game... you would pay out because I`m correct part of the way through game..

So if you placed a bet that BZ would score a goal, and he scored a hat-trick, you wouldn't go an collect your bet

Obviously if you asked Bobby how the game went, he'd say he scored 3, he wouldn't say 'I scored a goal, and then 2 more', but he did score a goal and the bookie would pay. And if asked 'Did you score a goal?' he'd say 'yeah, I scored 3', he wouldn't say 'no'.

 

[Gullflyinghigh]

I opened this thread thinking the only solution is the exceedingly obvious answer.

After a mild headmelt and some confused squinting I've come to the conclusion that I'm not only happy to carry on thinking that, I also have no interest in finding out why I'm wrong.

Up yours probability!

 

[Easy 10]

I have nothing to add to this monster thread, except to say - how in the name of holy hell can any of you be BOTHERED with all this ??

 

[Arthritic Toe]

yes ...so if he had stopped at one for the weekend you would have been correct but he didn`t he scored three...I`d love you to be a bookie I`d bet on 0-0 every game... you would pay out because I`m correct part of the way through game..

I'm not arguing that its true - I'm arguing that it has 2 interpretations. Lets soften the example a bit:
"Bobby will get a goal this weekend"
When he gets the hattrick most would argue that my prediction had been correct. However a pedant could argue that he didn't get "a" goal, he got several, and that my prediction was wrong. However my prediction was ambiguous.

 

[JoePrecious]

Here you go:-

https://en.wikipedia.org/wiki/Boy_or_Girl_paradox

Everyone is right and everyone is wrong!

 

[hans kraay fan club]

I have nothing to add to this monster thread, except to say - how in the name of holy hell can any of you be BOTHERED with all this ??

Beligerence.

 

[hans kraay fan club]

Here you go:-

https://en.wikipedia.org/wiki/Boy_or_Girl_paradox

Everyone is right and everyone is wrong!

No - I am right, because I've been arguing all along that it is ambiguous and that both interpretations are 'correct'.

 

[Diablo]

So if you placed a bet that BZ would score a goal, and he scored a hat-trick, you wouldn't go an collect your bet

The bet was he would score one goal.......which is specific...... A bet to score a goal would pay if he scored one or more...

 

[GT49er]

Ignoring the possibility of it being a trick question, or there being identical twins etc, someone has two children, and we're being told that one is a boy, the chance of the other being a boy is 50% - but you disagree, right?

No - not at all. Read my posts #30, and #42. I've said the same as you - that the answer to that simple question is irrefutably 50%.

It's 50% Do you disagree?

Yes

Statistically, it is EITHER 50% OR it is NOT 50%. It can't be both!

And although the original question is not well worded, it definitely states that one of the children IS a boy, not will be, or might be.

 

[Arthritic Toe]

..... A bet to score a goal would pay if he scored one or more...

but he didn't score "a" goal he scored several. You have just hoisted yourself by your own petard.

 

[hans kraay fan club]

Statistically, it is EITHER 50% OR it is NOT 50%. It can't be both!

And although the original question is not well worded, it definitely states that one of the children IS a boy, not will be, or might be.

Silly post because you've quoted my answers to two entirely different questions.

 

[Triggaaar]

No - I am right

because I've been arguing all along that it is ambiguous and that both interpretations are 'correct'.

Most agree the original question is ambiguous, but you still try and argue that my very straightforward example with 4 couples has a 1 in 3 chance of the 2nd child being a boy (in the example) and you're wrong. There's no ambiguity there.

EDIT - I see you've been back and done some sneaky editing to your answer to my example of 4:

(and yes, I DO understand your logic that only half of the b/g couples may have answered 'b' - I just don't take that same premise from the original question)

You should. Why have they told us one was a boy, why didn't they tell us one was a girl?

 

[hans kraay fan club]

Most agree the original question is ambiguous, but you still try and argue that my very straightforward example with 4 couples has a 1 in 3 chance of the 2nd child being a boy (in the example) and you're wrong. There's no ambiguity there.

It's your fixation with the '2nd child' that is preventing you from seeing the alternative logic, I think. Its (at least) one of them - not that one IS a boy and what is the other. That is along the lines of your coin question, and is obviously 50%.

Anyway, far more emminent mathematicians than you or I had decreed that both answers are valid. I'm happy to go with that.

 

[Diablo]

but he didn't score "a" goal he scored several. You have just hoisted yourself by your own petard.

"a" is the indefinite article........I`m over and out on this one we`ll have to agree to disagree,

 

[GT49er]

Silly post because you've quoted my answers to two entirely different questions.

Not really. It does make your apparent contradiction show how daft this argument has got!

 

[hans kraay fan club]

Not really. It does make your apparent contradiction show how daft this argument has got!

It has.

But there's no contradiction at all, in the quotes you posted, if you read them in context.

 

[Megazone]

What about hermathruidites?