EPTPuzzleing Question! (HARD) - Page 36
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Alpha
France1495 Posts
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wAt-74
United States137 Posts
On November 22 2004 12:21 Alpha wrote: did u already aked him? maube i can ask some of mone too like i said i have a meeting with him an hour from now. My long ass post i just posted, i havent asked anyone bout it yet, but i'm sure its true though | ||
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Alpha
France1495 Posts
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MoltkeWarding
5195 Posts
On November 22 2004 11:59 wAt-74 wrote: Hey guys about the boy and girl puzzle the answer IS 2/3. I'm double majoring and one of my majors is probability & statistics and this is a problem that you get in a beginning class. Lemme try to break it down a bit. you are given the fact that you know one of the childs genders, which is a girl. Now you want to find the probability that the other child is either a boy. You can break down this problem into a simple equation: P(the other child is a boy | given that at least one child is a girl) = P(having a girl and boy)/ P(having at least one girl) < -- there is a long proof for this equation but i dont think you would want to hear it. Trust me its true, all statisticians now it, its a basic equation and you can find the proof in any basic statistics book. so what is the probability of having a girl and boy? well your choices are... GG BB GB BG so P(having a girl and boy) = 2/4 // BG GB whats the probability of having at least one girl? P(having at LEAST one girl) = 3/4 // GG BG GB you plug it into the equation and you get (2/4)/(3/4) = 2/3 (if you cant do the division, use a calculator :p) Some people here think BG GB are the same when they are not. Both come in different order and that is very important to accept it. Here is a visual: EDIT: forget the visual i cant get it to line up properly... new visual:1st you have G-->G or G-->B or B-->G or B-->B As you can see they are different, i hope tat helps Oh btw haha GG is still the same as GG(same goes for BB) If you still dont believe me ask a statistician or stats professor about this, its pretty simple he/she should confirm this. AND if you still dont believe me then go to college and spend thousands of dollars so you can solve this. AND BTW: this is a great thread and keep them coming!  If order matters then GG can be inversed. If order doesn't matter GB and BG are the same. Let's look at the no order option: There are 2 kids. Three possible combos 2 girls 1 boy and 1 girl 2 boys Eliminate 2 boys and you're left with 2 girls and 1 boy 1 girl Let's look at the order option: You have G1G2, G2G1, B1G1, G1B1, B1B2, B2B1 Why can G1G2 be inversed? Follow my above post. Girl Girl: Girl answers door 100% Girl Boy: Girl answers door 50% Boy Girl: Girl answers door 50% Boy Boy: Girl answers door 0% Therefore GirlGirl=GirlBoy + BoyGirl | ||
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PhiGgoT
Vietnam151 Posts
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Melloweitsj
Norway118 Posts
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wAt-74
United States137 Posts
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MoltkeWarding
5195 Posts
On November 22 2004 12:35 wAt-74 wrote: hey warding i did read your post.. i wish i could explain it in person because if i just post it whatever i say, something will be lost in the translation because of the internet. But when you have a child its can only be either girl or boy. Theres is no such thing as girl1 or girl2. There is 2 genders girl and boy, well i'm not considering the "gray" aread in between. Thats why GG is still the same either way. I think this problem comes down to either you believe that this problem involves permutations or combinations. If you think combinations then the only choices are BB GG BG & if you think its a permutation then the choices are BB GG BG GB. Keep this debate coming i need to get pumped up for stats class, i have a quiz coming up Let me try to wind this up. The question explicitely states: The first child you see is a girl. What are the chances that the second child is a boy, correct? Before you knew that one was a girl the BG/GB/BB/GG split was 25/25/25/25. 2 girls = 25% 1 boy 1 girl = 50% 2 boys = 25% However, AFTER you know that one is a girl, BG <---She can only be one girl here GB <---She can only be one girl here BB <---she cannot be either here GG <---She can be EITHER girl here Do you see how GG has the same odds as BG and GB combined? 2 Girls = 50% 1 Boy 1 Girl = 50% I think you are confused because in algebra g=g. Therefore GG = GG. However, BG = GB. In the case of 2 G's, theres the potential for 2 different positions. Let us say that 2 parents have decided Their first son will be named Mark Their second son will be named Joe First daughter will be named Anna Second daughter will be named Krista (order matters) Possible Combos: Mark Joe Mark Anna Anna Mark Anna Krista 25/25/25/25 right? THe girl you saw, has 3x better chance to be Anna than Krista. We know that there is no Joe. Therefore presuming you saw Anna, the possible arrangements are Mark Anna, Anna Mark and Anna KRista HOWEVER IF you saw Krista, it adds another possibility doubling Anna Krista. You can claim: Referring back to the original statement, Anna Krista only = 25%, therefore 12.5% chance that you saw Krista. We know that this is not true, because there is a 25% Chance that you saw Krista. | ||
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BigBalls
United States5354 Posts
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BigBalls
United States5354 Posts
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wAt-74
United States137 Posts
 But i might have to wait,i have to go to class soon lol all i can think about its this damn puzzle now | ||
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Deleted User 3420
24492 Posts
im so fucking out of it i gotta go to bed omg | ||
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Catyoul
France2377 Posts
On November 22 2004 11:59 wAt-74 wrote: Hey guys about the boy and girl puzzle the answer IS 2/3. I'm double majoring and one of my majors is probability & statistics and this is a problem that you get in a beginning class. Lemme try to break it down a bit. (bla bla bla) I seriously hate to resort to authority arguments, but if you want to come to that, I've been through more years of college and maths than most of the posters here. I've done loads of probability and stats (I mean serious ones, not high school level like this one)... though it is of course absolutely irrelevant here since it's such a basic problem and the misunderstanding comes from the modelling. Again, the wording is absolutely critical, the math is trivial afterwards. You are answering the following problem : considering 2 children whose sexes are unknown. If you are given the information whether one of them is a girl, what is the probability of the other one being a boy? That is NOT the same problem he asked. His question is : you have 2 children. You see the sex of one of them, what information does it give you about the other one. It is ABSOLUTELY different. If you are not convinced of this, look at the different cases, and let's assume you are shown the sex of the 1st one : GG : 1st problem, you are told one of them is a girl. 2nd one, you see a girl first. Same shit ? GB : 1st problem, you are told one of them is a girl. 2nd one, you see a girl first. Same shit ? BB : 1st problem, you are told none of them is a girl. 2nd one, you see a boy first. Already not quite the same shit. BG : 1st problem, you are told one of them is a girl. 2nd one, you see a boy first. Absolutely not the same shit. I suggest you go read my answer of where the mistake comes from on bottom of page 8, or more detailed on page 10, or an explanation of the difference between the 2 problems on page 12... or one of the myriads of very correct posts in the thread by very nice people. | ||
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wAt-74
United States137 Posts
I really dont care if i'm right or not now, before i did, but now i want to find the correct answer if there is one. | ||
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lastas
Sweden1219 Posts
--------------------------------------------------------------------------------------------------------------------- Wow, you all suck. Actually when a baby is born its 52% to be a boy, so that would make the other kid more than 52% to be a boy, since when she got that 48% girl, she is now statistically even more likely to get a boy. ---------------------------------------------------------------------------------------------------------------------- | ||
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KarlSberg~
731 Posts
On November 22 2004 12:16 wAt-74 wrote: i go to Santa Clara University and San Jose State University. Oh man if i'm wrong, then i should get shot because probability is my MAJOR hahaa... i have meeting with one of my stats professors in an hour, i'll ask him about this too and see what he says Please don't shoot yourself for being wrong. The answer is 1/2. I studied math for the 24 years of my life and know many many people who did too, and I can swear being able to answer this problem has very little to do with studying a lot. Some people are just good at probability ridles. I am :-p | ||
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MoltkeWarding
5195 Posts
On November 22 2004 13:21 KarlSberg~ wrote: Please don't shoot yourself for being wrong. I studied math for the 24 years of my life and I can swear being able to answer this problem has very little to do with studying a lot. Some people are good at probability ridles, some aren't. Actually I thought that a 3 year old with no knowledge of math has a better chance of getting this question right than a probability wiz. Just comes to prove Schiller's assertion that modern sophistitry makes us all dumber  | ||
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Catyoul
France2377 Posts
On November 22 2004 13:18 wAt-74 wrote: hey Catyoul, i wasnt trying to throw around education as a means of saying i was right and everyone was wrong. i was stating it so that when people who read my post didnt think i was pulling stuff from my ass or something. I havent read your ppost on page 10 or 12 i think(i will), but i am going over the problem again because when i did the problem in my head i was doing it based on other peoples post and i want to read the original question more carefully. I really dont care if i'm right or not now, before i did, but now i want to find the correct answer if there is one. Sorry, reading my post again, it may have sounded agressive but it was absolutely not my intention. I'm just very tired so I'm noticeably harsher and more direct in my posts, no offense intended  On November 22 2004 13:20 lastas wrote: Wow, you all suck. Actually when a baby is born its 52% to be a boy (...) You're, like, talking about that hypothesis : On November 21 2004 23:21 Catyoul wrote: 1. the 2 children are 2 separate events. Those events are independent (well, I don't know if it's 100% true in biology, I guess it's pretty close at least but anyway we're working with the 50/50 model of getting a boy and a girl). :p | ||
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KarlSberg~
731 Posts
On November 22 2004 13:22 MoltkeWarding wrote: Actually I thought that a 3 year old with no knowledge of math has a better chance of getting this question right than a probability wiz. Just comes to prove Schiller's assertion that modern sophistitry makes us all dumber I insanely love maths and probabilities, but always hated lessons about it. Learning theorems makes me sick, but Maths can be a pleasure if you get to understand things by yourself instead of eating properties and definitions. Actually in a way knowing about probabilities can in that case be misleading since the problem looks like a classic (and tricky) problem, but in this example the answer is what it first seems to be. | ||
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lastas
Sweden1219 Posts
On November 22 2004 13:26 Catyoul wrote: You're, like, talking about that hypothesis : 1. the 2 children are 2 separate events. Those events are independent (well, I don't know if it's 100% true in biology, I guess it's pretty close at least but anyway we're working with the 50/50 model of getting a boy and a girl). :pyou're right, sorry for not reading through 30 pages, where half of the posts/posters are total blankminds ;-P | ||
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