statistics forum
- 2
How ironic is it that I'm playing qtoro instead of studying for my stats midterm and yet here I am answering stat questions still!
- 39
8aaron is correct that girl-boy combination is more likely (50%), while only 25% of two-child families will have both boys, and 25% will have both girls. now that the question says that you meet a boy on the street, it now is equally likely that he will have a brother or a sister. this is because two boys in a family means that you must weight that family double (because you're twice as likely to meet a boy from that family, because there are two boys). so now the chance is 50-50 that you'll me a boy from a family with two boys or a family with a girl and a boy. but i still don't think the explanation given is correct (just because there are two choices, boy or girl, that doesn't mean that both choices have the same weighting).
Oh man, first I was arguing against the paradox, but now I have to argue for it. It actually works out...
Here's another way to think of it. What is the probability of any given gender combination in a two child family:(25% BB) - (50% GB) - (25% GG)
We can ALL agree on that, it's simple math. All the paradox problem does is remove the GG possability. The probability of BB becomes 33%, and the probability of GB becomes 66%. Cenus data bears this out: about 50% of families are GB, making it 66% when you discard the GG families. Can't think of any other way to clarify this.
It doesn't work out at all!
Each is an independent event.
The probability that child 1 is a boy is 100% (because you've met child 1).
The probability that child 2 is a girl is 50% (equal probability boy or girl).
So the probability that, having met a boy, that his sibling is a girl is:
1*1/2 = 1/2.
That is it! That is the only answer. I asked 2 of my old stats professors, and I trust them more than peeps on this site. Plus I consulted my old stat book and prob theory book. This is the mathematical way to solve this problem.
People are getting caught up in the language, and not looking at the underlying math. Being a girl or boy is an independent event with 1/2 probability. That means, NO OTHER EVENT effects it. This is not like having 4 kids and pulling 2 out - becuase you don't have 4 kids. You only have 2 kids, each one iwth 50% probability of being a boy or girl. You don't have a set of 4 to start with, only a set of 2.
I understand what you're saying, and I'm not even going to try and explain WHY the probability works out the way it does, but if it's true that 50% of two-child families with at least one boy have one girl, then we conclude: 50% BB and 50% GB, Correct? The inverse would have to be true of families where at least one of the children is a girl: 50% GG and 50% GB. The GB in each case MUST be referring to the same families, therefore if we combine these results we have: 33% BB, 33% GB, and 33% GG in the general population. That's simply not how the world is, we know the true breakdown in the population is 25% BB, 50% GB and 25% GG. The math just seems funny because 25% of the possible outcomes are being disregarded in the paradox problem.
Oh, and your statement "So the probability that, having met a boy, that his sibling is a girl is: 1*1/2 = 1/2." is absolutely correct. Unfortunately it does not disprove the paradox, which is asking a very different question. The problem with your statement is that if you randomly meet a boy, BB families are twice as likely to be represented than GB families. Though the probability that a boy has a girl sibling IS 50%, the probability that a FAMILY with a boy also has a girl is 66.6%
So read my question again and explain how my explanation is correct but answer is wrong?
I am asking that, given 1 boy, the other child is a girl. You're talking about how many combinations of 4 children end up GB. Two different questions, no? One is about a probability in a set of 2 (my question). The other is about a percentage of results for a set of 4 (your question).
The way your question is worded, 1/2 is the correct answer. The question you are asking, however, is not the paradox question that you are trying to disprove with your explanation. The paradox question would be "if you meet a FAMILY on the street with two children, one of whom is a boy, what is the probability that the other is a girl?" The answer to that question is 2/3.
- 2
Not all IQ tests have a standard deviation of 15 points. Wikipedia agrees: http://en.wikipedia.org/wiki/Iq#IQ_Test_Structure
the above number only count contries the UN register passes its cencsus around in, which is not including all of the Islamic state countires
sorry, im sure its muslim, bout 2 billion christains over 9 billion muslims.
i'm islam =)
im hindu why couldnt it be hinduism almost all of indians are hindu
ima christian!..
i thought that Buddhism is Largest religion TT
I thought I read something that said Islam has taken Christianity's crown..fu oh well
unashamed proud christian ;]
i'm buddhist
I'm Buddhist.. ^^
I'm Christian:)
gys
proud Christian;)
... i'm catholic, and i thought it was buddism
ima proud christian :3
so obvious..easy...
i thought it's Islam
i thought it's Islam
i mEANT to click christian still [sell ur soul]
yes... christian...
yay!
duhhhh
who wouldn't know this...
i'm a catholic
BS! IT should be Buddhism.
Yay! I am Christian! Love Jesus Chirst!
damnit. well, i'm not religious, so... >_>;
easy
oh. i thought it was islam...
ahahahahaha God - oops
:)
oh haha oops didnt read the whole thing! xDDD
confucianism ftw woot
actually i heard Islam will be the largest religion in the world
YES
^^ Godbless
Those who hate this question.....may u be blessed!!!
ha, in a sense, elforslund, thats true..
Yet the main reason why is because they have spent millenia forcibly converting people, burning wthces, heretics, crusades and anybody who didn't swallow their truth. Sure, if you bully eough people... you're gonna make it to the top of the pile.
booo
God Bless
antitheism! ._. no god
i sure wish everyone had only this one religion...
God Bless! ^____^
=)
You would've had to live in a hole all your life not to know
Yay!
yah...the relegion is beautiful but the people aren't really living it out right..even i ..
You'd have to be living under a rock to not know.
spiritualist...si u can just count out formt he christinality
lol whoa christianity is goin far..im still spiritist
u guyz are all wrong..............its confucianism...........lol
aahhh SPIDER EEKKKK!!! i mean uhmmHaii ^^
what? why would you say that? learn some respect kiddo!
That's right -- and it will stay this way!~
Christianity???
um as long as it's not scientology i think we're good
iKyoxTohru ...what you said is true.
sorry heard from class^.^
<3
no it changed this year
<3
Its not Islam KiwiShim. Christianity is the largest, with Catholism as the largest denomination.
Minus me.
what the...no comment la..
Islamic is the second largest, no? But I'm Catholic-Christian, so I don't really know. >>; I just think I heard this in Social Studies when we were studying world religions.
unfortunately...
It's Islam...retard.
Christianity is the religion with the largest number of professed religious ... are more Christians than any other religion, in terms of both people and assets.
... no comment
Buddhism is becoming large, too.
yay christians rullz!!
really?
really is buddhism...