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Old 06-10-2008, 12:26 PM   #1
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Bob has two children. One of his children is a boy. What are the odds that bob has a daughter?
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Old 06-10-2008, 12:52 PM   #2
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2/3
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Old 06-10-2008, 01:02 PM   #3
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assuming neither child is hermaphroditic, i still need more information to answer that question. which one is the transexual?
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Old 06-10-2008, 01:17 PM   #4
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Originally Posted by lazygood4nothinbum View Post
assuming neither child is hermaphroditic, i still need more information to answer that question. which one is the transexual?
Bob, obviously.
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Old 06-10-2008, 01:33 PM   #5
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50/50.
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Old 06-10-2008, 01:42 PM   #6
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Nearly 2/3. It would be 2/3 except that the actual chances that any given birth is a girl is not 50%, but about 48.8% (a 100 in 205 chance, since about 105 boys are born for every 100 girls).
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Old 06-10-2008, 01:50 PM   #7
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mutually exclusive events so stats on births will prevail
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Old 06-10-2008, 01:55 PM   #8
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There are four possible outcomes for Bob, and to make it simple assume births are 50% boys and 50% girls:

* boy and then girl
* boy and then boy
* girl and then boy
* girl and then girl

If we know nothing, each of these have a 25% likelihood. But knowing one is a boy, we can remove the girl/girl possibility and we are left with three options, each with a 1/3 chance of occurring:

* boy and then girl
* boy and then boy
* girl and then boy

So in 2/3 of the scenarios, Bob has a girl.
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Old 06-10-2008, 02:22 PM   #9
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nice, didn't catch on to the elimination requisite
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Old 06-10-2008, 02:32 PM   #10
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If we know nothing, each of these have a 25% likelihood. But knowing one is a boy, we can remove the girl/girl possibility and we are left with three options, each with a 1/3 chance of occurring:
Say you pick a parent of two, Sue, at random. You ask for the sex of one of her children. According to your answer, there is a 2/3 chance that the sex of the second child is the opposite of whatever Sue answers. If she says she has a girl, odds are her other child is a boy. If she says she has a boy, odds are her other child is a girl.

But if Sue has two boys, she will always say she has a boy. If she has two girls, she'll always say she has a girl. And if she has one of each, she'll pick one at random and say that. In all of those cases, the odds are equal--one in two--that her two children are the same sex.
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Old 06-10-2008, 03:15 PM   #11
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The odds that bob has a daughter are 0% (zero percent/nada/zilch/no way Jose).

What assumptions have I made?
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Old 06-10-2008, 03:38 PM   #12
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The children are not his.
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Old 06-10-2008, 03:41 PM   #13
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Originally Posted by CuppaJoe View Post
The odds that bob has a daughter are 0% (zero percent/nada/zilch/no way Jose).

What assumptions have I made?
I don't know about your assumptions. Perhaps one of the following:

His wife "had" the kids.
Nobody owns a kid.
You know bob personally.
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Old 06-10-2008, 03:49 PM   #14
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I'm glad I don't have kids. Bob can have as many as he wants.
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Old 06-11-2008, 12:43 AM   #15
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Originally Posted by Abreutime View Post
I don't know about your assumptions. Perhaps one of the following:

His wife "had" the kids.
Nobody owns a kid.
You know bob personally.
You and Ronin are thinking out of the box, cool. I didn't think of those 4 assumptions. I was being literal.

No, I don't know him personally. I assume you made him up. In case the 0% solution is 100% wrong, throw me a bone: This family of four is hypothetical, right?

Sorry, that was off point.

Has anyone else inhaled the coffee dust and crashed to zero?
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Old 06-11-2008, 09:44 AM   #16
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I was thinking kidnapper pedophile, but didn't want to stress you parents out.
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Old 06-11-2008, 09:58 AM   #17
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Quote:
Originally Posted by Abreutime View Post
Bob has two children. One of his children is a boy. What are the odds that bob has a daughter?
First assumption: Abreutime has made no typos in the original post, therefore there are two "Bobs," uppercase Bob and lowercase bob. Next assumption: bob is Bob's son. bbbam1 is so right and a riot in saying "Bob can have as many as he wants." I also agree with P.K. Sublime, "the stats on births will prevail." Assuming bob is "a boy," he has not yet hit puberty and therefore has no children.
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Old 06-11-2008, 10:03 AM   #18
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I was thinking kidnapper pedophile, but didn't want to stress you parents out.
Our last two posts crossed on the net, thanks, I was still coping with hermaphrodites and trannies. This is just like retirement planning, now I need to re-think the assumptions which intersect and crash into the unknown.
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