/biz/ - Business & Finance

>>12295142
Never send your daughters to answer the door. There could be a nigger on your porch

50%

>>12295142
it is 1/(current amount of genders registered by the LGBTIQCAPGNGFNBA)
thank you xir, where do i pick up my diploma?

(ii) if they sent the elder daugther to the door it 100% means they have another daughter, otherwise they'd send the boy

This question is offensive OP. Do you not respect pronouns or something?

It's 50%, the age of the daughter has nothing to do with it

>>12295153
1.45% since there are 69 possible genders

why am i not surprised to see biz resorting to memes to cope with the fact they cannot grasp probability theory. also there are 2 questions to solve and biz does not know how to solve either 1.

>>12295142
1. 33%
2. 50%

>>12295232
*1. 66%

>>12295225
The possibilities are:

GG
BG
GB

Correct? BB is ruled out in both scenarios because the daughter answered the door? And since GB and BG are the same, that leaves GG and BG(GB) which is 50%

>>12295232
>>12295244
>t. brainlet

>>12295142
No gender is ever mentioned so it's 50% both answers.

>>12295152
FPBP OP BTFO

>>12295184
That's basically what I said

>>12295142
(i) 50%
(ii) 25%

>>12295225
You're getting memes because your bait is so bad you can't even bait the lowest IQ board on 4channel.
Reasses your life choices.

>>12295283
Not just that but we don't know if the daughter identifies as a daughter, son, aunt, uncle

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

(i) 1/2
(ii) Intuitively I feel it's 1/2, there could be some monty hall element to this making it 1/3 but I don't think so.

>>12295152
FPBP OP BTFO

>>12295152
FPBP OR BTFO

>>12295152
FPBP OP BTFO

Why do these retarded ass mutual exclusion problems always surface such brainletry on /biz/.

>>12295225
>goes on biz
>doesnt ask a biznes or finance question
>upset that no one answers

>>12295152
FPBP OP BTFO

>>12295142
The gender of one child has no influence on the gender of the other child. It's 50% in both cases. This one was boring.

>>12295152
FPBP OP BTFO

>>12295142
1 is E(x) or ~63%

>>12295152
FPBP OP BTFO

thanks just bought 100k

>>12295244
This is correct

there are more than 2 genders, so its endless.

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295142
1) 1/3
2) 1/2

next fag

>>12295152
What kind of reddit tier replying bullshit is this

>>12295593
/biz/ is 90% reddit refugess. Didn't you know that?

>>12295152

FPBP OP BTFO

>>12295142
I) 50%, other child could be a boy or a girl
II) 50% again, other child could still be a boy or girl

Is biz really that retarded?

>>12295366
I think there is a monty hall thing going on with the second part. First is clearly 50%.
G -> G
G -> B
B -> G
B -> B
Lower two are eliminated since we know the oldest is a girl.
G -> G
G -> B
Since we don't know if the daughter answering the door is younger or older the above possibility has a 100% rate of showing girl while the below has a 50% rate of showing girl. Like the balls puzzle this means 2/3 chance the other daughter is a girl or 50% for part 1 of the question, 66.7% for part 2.

Of course this is disregarding the 90quintillion possible genders.

>>12295679
Correction the question is asking for the chance that the other child is a boy which means 1/3 for the second part

>>12295366
You know for a fact they have a girl so if it's the younger daughter who opens the door then it's 100% the other child is also a girl.

In the first one it doesn't matter the gender of who opened the door.

>>12295679
Jesus dude I really hope you're trolling

>>12295670
Nah math is retarded. the modern accepted answer is something else.

>>12295679
We don't know the oldest is a girl

0%, nobody who was married with children would ever invite me over to their house

>>12295152
FPBP NIGGERS BTFO

>>12295679
i and ii and independent.
The fact that the daughter is eldest is irrelevant information. The fact that a daughter opens the door is irrelevant info. The fact that there's 2 kids is irrelevant info. Is a child born boy or girl is an independent event unrelated to anything else.
There's so much irrelevant info here it's clouding your judgment.

The question is basically "what is the probability a child is a boy". The question is basically the same for both i and ii. The child can be boy or girl.

50%

>>12295759
the absolute STATE of /biz/

>>12295711
Look up Monte Hall, gets people completely convinced the answer is obvious this is a rehashing of the problem with 3 pots and 2 gold balls in 1, 2 silver balls in 1 and a gold and a silver in the third. You think the answer is obvious so you underthink it.

Think of it this way, if the house has 10 million boys in it and one girl or 10 million girls in it and no boys and you open the door and see a girl what are the odds you're in the first possibility as opposed to the second?

>>12295730
What are you talking about lul

Probably

There are 4 ways you can have two kids:
1. boy, then another boy.
2. boy, then girl
3. girl, then boy.
4. girl, then another girl.

i) A girl answered the door, so case 1 is eliminated. In what is left, you have a 2/3 chance of a boy.

ii) The eldest is a girl. That means only 3 and 4 applies to the situation. In which case, the other child has a 1/2 chance of being a boy.

And that's my final answer.

>>12295142
i) 2/3

ii) 1/2

I'm glad there are so many dumbfucks on /biz. If you guys weren't here, I wouldnt be able to make my money

>>12295780
You're making the problem more complicated than it is. Since you don't know whether the girl who answered the door is the older your younger sibling, you have zero information pertaining to the gender of the other sibling. Therefore it must be 50%.

>>12295771
Explain then, since all you can do is answer with jokes and memes

>>12295759
This is what tricks people they think that age can't be relevant information. Yes the sex of the child is an independent event, but we don't know the sex of the child, and the likelihood that a person is one thing or another changes with circumstantial evidence. If the oldest child is a girl then the youngest must either be a boy or girl with equal likelihood.

GG vs GB

However while the likelihood of either scenario occuring is equal, there is a 100% chance that a girl will answer the door in scenario A and only a 50% chance that the girl answers the door in scenario B. Since a girl has now answered the door it is slightly more likely that we are in scenario A.

Unfortunately this is too difficult for low-normal IQ types to comprehend so every time one of these threads gets dropped you just have to accept that brainlets aren't going to be able to understand probability.

>>12295804
Thank you for this explanation.

>>12295844
>>12295804
This is really amusing

>>12295824
I know you think that, but if you just look this up you'll see many very good explanations. You think i'm making it more complicated than it is because you're not using the available information to derive likelihood.
>You have zero information pertaining to the gender of the other sibling
We don't know which sibling we're looking at to begin with and you don't need to KNOW which sex the other sibling has, the question isn't which sex IS the other sibling it's asking how likely they are to be one sex.
>Therefore it must be 50%
"We don't know therefore it must be 50%" is like saying that you have a 50% chance of winning the lottery because you don't know if you'll win or not.

>>12295844
I simply don't understand how the sex of one child affects the potential sex of the other.
The probability of a child being a boy is 50%. The fact that they have another child who may be a boy or a girl is irrelevant. The fact that we know they have a girl in scenario ii is irrelevant. It's not like after that had a daughter, they were more inclined to have a boy next time around.
Imo the sex of a child is completely independent of everything which is why I think the answer for both scenarios is 50%.

>>12295804
But it's more likely that you're looking at a 2 girl house because a girl answered the door. If the door wasn't opened then it would be 50/50 but if we've seen a girl then there are 3 possibilities.
1. We're seeing the older girl in GG
2. We're seeing the younger girl in GG
3. We're seeing the older girl in GB
And all of these possible situations are equally likely.

>>12295883
>We don't know which sibling we're looking at to begin with and you don't need to KNOW which sex the other sibling has, the question isn't which sex IS the other sibling it's asking how likely they are to be one sex.
They are mutually exclusive.

>"We don't know therefore it must be 50%" is like saying that you have a 50% chance of winning the lottery because you don't know if you'll win or not.
If the lottery was a coinflip then yes, you would have a 50% chance of winning. Gender is a coinflip, and one child's gender does not influence the other child's gender.

>>12295886
Think of it this way, you have two households.
H1 contains 1million girls and 0 boys
H2 contains 1million boys and 1 girl
You open a door and a girl answers
Are you as likely to be in H2 as H1?

>>12295910
Seriously look up Monte Hall, you still probably won't be able to understand but atleast you'll be worth replying to this shit is why this whole forum are cryptogamblers

>>12295908
I see you're talking about question i).
Why are you counting GG twice? It's only 1 item in the sample space. And you forgot BG.
So it would be GG, GB and BG in the sample space.

>>12295908
The fact that we've seen a girl is irrelevant. The gender of the next child has nothing to do with the gender of the first child. No doctor in a hospital will ever say "what's that, you've had 4 daughters in a row? well then it's time you've had a son this one will definitely be a boy." Sex of a child is a coin flip, 50/50. Everytime.

>>12295932
That's a screwy scenario. I know it's just an example but the odds of having 1 million girls and 0 boys is (1/2)^1000000. This would never happen. There should be about 500k boys and 500k girls, in which case it's about 50/50 what gender opens the door.

>>12295932
That scenario literally has nothing to do with this question. We know there are only two siblings, and we only know that one of them is a girl.

>>12295936
I know what the monty hall problem is. It's unrelated because we only have two options here, not three. Now go look up gambler's fallacy.

>>12295593
This thread is the final blackpill. /biz/ has been taken over by faggots and crypto is dead. I finally have the courage to leave.

>>12295142
Both are 50%.

>>12295232
>>12295244
>>12295256
>>12295804
>>12295908
You are all fucking brainlets. No wonder you lost all your money on shitcoins.

There are 4 possibilities
GB, older answers door
BG, younger answers door
GG, older answers door
GG, younger answers the door
2/4 of those possibilities leads to the other being a boy.

>>12295982
>The sex of a child is a coin flip
Yes I am aware and have not once disagreed with this no I have no idea why you keep bringing it up.

It's the perfect scenario for this example, it demonstrates that if there is a higher percentage of girls in one theoretical house you are more likely to be looking at that one. Saying "this would never happen" does not change the validity of these circumstances and while you can't understand the others I know you can understand these.

Saying "this would never happen" is a cop out in a math problem and you know it. I'm just demonstrating how when you change the percentages even further the gap in likelihood gets even bigger.

>>12296023
I think i'm leaving too, there used to be some really bright people on here but these days they can't even look up the answers to math problems and shit on google, the advice here was never really worth trusting but it really is a reddit.biz now.

Both questions are about an unknown with two outcomes. We have no information relevant to the probability of the outcome of the unknown.

It's not a monty hall problem. It's a disguised coin flip problem. 50%.

>>12295142
>Hint: Define your sample space carefully!
Guys ffs i can't belive you didn't see the OBVIOUS clue! 'A married couple has 2 children whom they have not met'
Its doesn't say they are together, if they haven't met there kids it means only 1 thing!

The kids are the children of niggers! Who fuckin cares about niggers!

Your welcome OP, this /thread is now closed!

>>12296048
>one coinflip influences the next coinflip
>this person thinks he has a superior IQ

>>12296048
You're a brainlet See >>12296036

>>12295908
Omg finally someone with triple digit IQ

>>12296137
>>12296163
Retards.
https://www.analyticsvidhya.com/blog/2017/04/40-questions-on-probability-for-all-aspiring-data-scientists/
>2) Alice has 2 kids and one of them is a girl. What is the probability that the other child is also a girl?

>You can assume that there are an equal number of males and females in the world.

>A) 0.5
>B) 0.25
>C) 0.333
>D) 0.75
>Solution: (C)

>The outcomes for two kids can be {BB, BG, GB, GG}

>Since it is mentioned that one of them is a girl, we can remove the BB option from the sample space. Therefore the sample space has 3 options while only one fits the second condition. Therefore the probability the second child will be a girl too is 1/3.

>>12296216
Retard.
https://en.wikipedia.org/wiki/Boy_or_Girl_paradox
>However, if the family was first selected and then a random, true statement was made about the sex of one child in that family, whether or not both were considered, the correct way to calculate the conditional probability is not to count all of the cases that include a child with that sex. Instead, one must consider only the probabilities where the statement will be made in each case.[12] So, if ALOB represents the event where the statement is "at least one boy", and ALOG represents the event where the statement is "at least one girl", then this table describes the sample space:

Equal occurence rates for all 4 scenarios because 50/50 on the sexes as brainlets love to say.
GG
GB
BG
BB
#1 50% boy in house
GG: .5 occurence rate of G
GB: .25 occurence rate of G
BG: .25 occurence rate of G
BB: Ruled out
#2 33% boy in house
GG: .67 occurence rate of G
GB: .33 occurence rate of G
BG: Ruled out
BB: Ruled out

>>12295932
Read this example again if you don't understand how you can be more likely to be in one situation as opposed to another based on what you are observing. Look up the boy girl paradox on wikipedia this is a rehashing of that for less ambiguity. An investing forum that doesn't understand probability is not a place worth spending time.

>>12296216
lul someone who has a clue finally showed up right as I was finishing good luck man

>>12296252
Brainlet.

>>12296262
Brainlet.

>>12296252
>An investing forum that doesn't understand probability is not a place worth spending time.
Sad and true. 2019 will be the year of nobiz for me.

>>12295194
wew, i came to say 56%, but this is way better.

But why are the different combinations of BG relevant?

An unknown human has a 50% chance either way.

>>12296319
You know for a fact the oldest ISNT a boy. Your calculation has to include this information.

>>12295152
FPBP OP Eternally BTFO and /biz/ redeemed

>>12296319
>But why are the different combinations of BG relevant?
They're not. This is what happens when people don't have an intuitive understanding of probability. They blindly follow formulas that they don't actually understand.

>>12296345
It's irrelevant.

>>12296345
But all that tells us is that the other child is younger. There's noting to calculate?

>>12295152
FPBP OP BTFO

>>12295142
1) 50%

2) 33%

G-B
G-G

Three different chances for a girl to open the door, with only one of them leading to a boy sibling. Therefore it's 33%.

>>12296385
Brainlet.

Yeah sorry dudes the calculations aren't even necessary. Imagine it was real life. It's 50/50.

>>12296362
Shut up idiot
>>12296375
Youre calculating the possibility that there is a boy in the house.

>>12296425
So we know the first is older and a girl. That has absolutely no bearing on the next child's gender. You don't need a formula. It could be a boy or a girl. So 50%.

>>12296375
>>12296397
Think hard about all possible scenarios that could happen. Write them all down and then you will have your probability. This type of question exists to expose the human lack of statistical intuition. Be better than 90% of the world and don't answer based on intuition but arrive at the correct answer with counter intuitive math.

>>12296425
>Shut up idiot
High IQ intellectual right here

>>12296468
Scenario 1: Parents had a boy
Scenario 2: Parents had a girl

>>12296468

It's basically the same as saying 'heres an unknown person, what's the likelihood they are a boy or girl"

Can you explain how the first child's gender has any bearing on the seconds? It doesn't.

Conservatism is the new counter culture.

Think about it. There is no way the gender of an unknown person can be anything other than 50/50.

How the fuck could it be 0.33 either way?

>mfw everybody in the thread thinks the likelihood of having a male child is 0.50 and the likelihood of having a female child is 0.50

>>12296504
Hey Im (ID: ECGQoEFX), just switched off my phone.

>Can you explain how the first child's gender has any bearing on the seconds?

The fact that at least one of the two children is a girl does not tell us anything by itself.
The fact that a girl opened the door does not tell us anything by itself.

But these two facts together allows us to learn something we couldn't have before.
Lets walk through the child combinations and all the scenarios that come with each:


Combination 1) Eldest is Girl, youngest is Boy
Scenario 1 of combo 1) Eldest doors, other is boy.

Combination 2) Eldest is Girl, youngest is Girl
Scenario 1 of combo 2) Eldest opens door, other is girl.
Scenario 2 of combo 2) Youngest opens door, other is girl.


So we have three scenarios in total, two of which lead to the other sibling being a girl, and one which leads to the other sibling being a boy. Therefore a boy is the other sibling in 1 of the 3 scenarios so the answer is 33%.

Im not trying to trick you with confusing math here. This type of stuff is counter intuitive but thats why its so important to recognize how easily we can be fooled and strive to do better.

>>12296587
>there are 9999 girls and 1 boy in a room
>what are the chances that a random person in the room is a boy
>HURR DURR IT MUST BE 50/50!

>>12296036
you're probably black
how can you not understand that a girl answering the door increases the probability that only girls live in the house?

>>12296645
>>12296598
Just wrote a simulation for this problem in Python. 1 million trials. Feel free to critique my code. https://pastebin.com/vgWuMAF8

Results:
Number of times sibling is a boy: 500434
Number of times sibling is a girl: 499566
Probability of sibling being a boy: 50.04%

>>12296598
I get what you're saying, but there are still only 2 possible outcomes.

>>12296719
You wrote an elaborate coin toss, nothing else

>>12296601
Retard alert

>>12296757
Exactly. That's precisely what the question is.

>>12296768
My dude, where is the door included?

(i): 2/3
(ii): 1/2

Consider N (just pretend N=100) families with 2 children. N/4 will have 2 girls, N/2 will have a boy and a girl, N/4 will have 2 boys. In (i) 2 boy-families are excluded, clearly the probability of at least one child being a boy among the remaining families is 2/3. In (ii) we consider families with the elder child being a girl (of which there are N/2). Among these families, the younger child can be a boy or a girl with equal probability.

>>12296719
I went ahead and codded it up properly for you.

Results:
Youngest is girl: 500714.0
Youngest is boy: 249972.0
Odds of youngest being a boy = 0.33299142384432373

Code: https://pastebin.com/YxYMzVY3

>>12295152
FPBP OP BTFO
/biz/ confirmed highest IQ board

>>12295142
2/3 for i
I don't quite get ii but I spent like 30 secs on it
Also these replies, this board is reddit as fuck

>>12296719
>>12296768
LUL
You wrote a different problem from the one presented then said "critique my code." You've gotta be trolling.

This would only work for the first half of the problem, you don't have the fact that the daughter is eldest anywhere in that you never even created a property for older/younger.

I've never written shit in python but you would need to define A as [older/girl] and B as [younger/variable(girl or boy determined by coinflip)].

Now after flipping a coin to see which sex the second child got you flip a coin to see which of the two answers the door.

Add an if statement that eliminates all results in which B answered the door as a boy since that situation isn't possible.

Of course you get 50:50 when you don't include the girl answering the door jesus christ.

Part a: Lets consider the order of appearance of children at the door, where we refer to a child as G1 for a girl who appears first, and B2 for a boy that appears second. There are 6 scenarios, in order of appearance at door. B1B2, B2B1, B1G1, G1B1, G1G2, G2,G1. First at the door is a girl, i.e., exclude first 3 possibilities. Thus, we are left with the possibility that the order of appearance of children at the door are G1B1, G1G2, and G2G1, i.e. the probability of other child being a boy is 1/3 since we are twice as likely to encounter a girl upon opening if the family has 2 girls.

Part B: Lets refer to older children as OX and younger children as YX, where X is the gender of the child. Thus, knowing that the gender of older child is girl, we have fixed one of the genders of the kids. By order of appearance, the possibilities are the following: (OG1YB2),(OG1YG2),(YG1OG2),(YB1OG2). There exist only these 4 possibilities since the older child can either appear first or second, and the younger child can either be a boy or a girl. Since the case YB1OG2 is excluded because first to open door is a girl, we once again arrive at having a 1/3 chance of other sibling being a boy.

Did I miss something? I can't quite see how the extra bit of information that the eldest child is a girl helps in this situation since we are already given that the child you first see is a girl.

>>12296858
Exactly, you can see the problem properly represented via code here: >>12296844

>>12296858
Holy fuck you got me doing reddit spacing
>>12296844
https://pastebin.com/YxYMzVY3
This guy included the door opening by going through the 4 of GG and GB opening the door and throwing out B opening the door since that didn't happen. Surprise surprise it's 1/3.

>>12295679
This is the right answer. See Monty Hall on Wikipedia for the explanation. You have to take into consideration in (ii) that you know one of them is a girl. Because she opened, the chance that the other one is also a boy is smaller. If you didn't knew, the chance is still 50% for the other child.

Fucking brainlets I swear. That this comment has no other respones proves you guys are fucking sub-nigger tier dumb and will never make it.

>>12296907
To add to that: assuming the eldest opens the door has nothing to do with if you think the eldest always opens the door or some shit. If that had to be the case, then it would've been mentioned. As well as girls/boy ratio is just assumingly 50/50.

>>12296844
Yeah I concede, I fixed my code to include scenarios where the boy opens the door and got the same result.

>>12295142
(i) 50%
(ii) 100%

>>12296943
Glad to hear it.

>>12295142
(i) 50%
(ii) 100%; Boys usually answer the door.

biz is fucking retarded

>>12295759
No, those are not irrelevant at all
>"what is the probability a child is a boy"
Jesus christ this is not a hard problem anon, that's not the question at all. There were conditions given. If you can't figure out how the conditions apply it doesn't mean they are irrelevant.

>>12295188
You're retarded. If you know the oldest child is a girl the youngest might open and be female. Thus it's a 75% chance the other child is a girl.

>>12296970
FUCK FUCK FUCK I hate making errors on this fucking site. I thought it said girl instead of boy.
(ii) 33%: The eldest daughter can be an older sibling to a younger boy, or to a younger girl, or to a girl of equal age which leaves chance at random odds. 1/3 of those options is being a boy which gives you 33.3333%
Boys usually answer the door.

>>12297001
67 actually.
You're saying its a 1/4 chance that the sibling could be a boy.

>>12296874
Part a can also be shown using Bayes theorem. We know that one of the kids is a girl, so to find the probability that one is a boy, we can find probability that both are girls and subtract that from 1. So, P(GG given G)= P(G given GG)*P(GG)/P(G). The probability that 1 is a girl given that they're both girls is 1. P(GG)=1/3, and P(G)=1/2. Thus P(GG given G)= (1/3)/(1/2)=2/3. Probability that the children aren't both girls is 1/3, thus, probability that one is a boy is 1/3

>>12295804
2/3 chance of a girl, you mean. You mixed up the problems. First one is about how they answer the door and not the order they were born.

In a girl-only household the chance a girl opens the door is 100%, meanwhile in a GB household the chance a girl opens the door is 50%. As such, there's 2/3 chance of another girl

>>12295142
2/3
2/3? I don't see how knowing the age would affect the outcome

>>12297038
You're dumb. Read the question.

>>12296943
Where's my apology?

>>12296737
Yes, we're calculating the probabilities of said outcomes
Holy fuck man

(i) 4 possible outcomes defined as {B+B, B+G, G+B, G+G} using the Commutative property of addition we can determine that B+G and G+B result in the same sum — therefore we can simplify that outcome to BG for short resulting in {B+B, BG, G+G}. When G answers door we can remove B+B resulting in {BG, G+G}. The chance of a boy being the other child is 50% in this case.

(ii) 2 possible outcomes defined as {BG, G+G}. Again we see a 50% chance of the other child being a boy.

If we were not working with sums in this case I would buy into the 33% solution but that is simply denying the fact that the word children is an aggregation (sum) of two or more prepubescent humans. A sum implies addition and addition must follow it’s laws.

some of you are trolling but im sure a lot of you are actually serious. this is the most retarded community ive ever encountered in my entire life

>>12296874
You're good, but for the first part you're forgetting that a family with 1 girl and 1 boy is statistically more likely to begin with.
GG, GB, BG, BB
in a set of two coinflips you're only gonna get the GG family 1/4 of the time whereas you'll get the GB family 1/2 the time.

The eldest child being a girl changes things since now we can go through
GG, GB, BG, BB and eliminate both BG and BB as opposed to just BB. The phrasing of this question is weird as hell though, and according to wiki there are a lot of ways for your logic in part 1 to be right depending on the exact puzzle, and i'm too burnt out of this discussion to go through it again.

Thank you smart people for helping me out of this thread I can sleep without wanting to kill myself now.

>>12297065
>2/3? I don't see how knowing the age would affect the outcome
Yeah, I'm not quite sure I get it myself. If he straight up asked what's the chance of another girl, sure, it's 50%, but the door condition is still there

>>12295804
Buddy, both case 1 and 2 are eliminated when a girl answers the door. It's a 50% chance.

The second question I think we can all agree age is irrelevant which means the two questions are:

>a daughter answers the door, what is the probability the other child is a boy?
>a daughter answers the door, what is the probability the other child is a boy?

It's the same fucking question twice. It's the same answer twice. And that answer is 50%, both times, assuming there are only 2 available genders (boy and girl).

The ONLY way this changes is if we assume for more genders than just boy and girl.

>>12296874
Yeah I don't see it either.
>>12297093
>>12296036
You've been acting like a retard the entire thread, and you got your answers wrong. Piss off.

>>12297219
Also this is assuming that there's a 50% odds of having a girl vs a boy which is missing information. In reality there are more men on the planet but this is affected by things like geolocation (e.g. countries where they kill baby girls because boys are more valuable) and many other factors so I think it's fair for the sake of this grade school math problem we assume a 50/50 odds.

>>12295142
51.2%
51.2%

>>12297219
The problem has already been solved with proof posted

Go read: >>12296844

>>12297237
No you are fucking wrong. If you are too much of a brainlet to even understand the sample cases even as they are explictly spelled out for you you have no hope.

>>12297120
Pretty sure this question is more similar to the bertrands box paradox than the Boy-Girl paradox

https://en.wikipedia.org/wiki/Bertrand%27s_box_paradox#Card_version

>>12297219
Nope. Either girl could answer the door in a girl only household. Only one girl could answer it on a boy-girl household. This tips the scales.
>>12297264
Explain how then. The other guy pulled Bayes.

>>12297296
His sample space did not include which child answered the door.

>>12297268
It is, yeah. Which is why ii doesn't really make sense, unless it's made to trick you.
>>12297309
Is your answer to i 50% still?

>>12297368
Yes, if you can't understand why, you have no understanding of probability. I didn't actually read the second question when I made my first post, the answer to that is 1/3.

>>12296036
you also brainlet.
the answer to 2 is 0% since you know that one children is a girl and the question is "when A daughter answers ..." not "when THE daughter answers..."

>>12296036
you're also brainlet.
the answer to 2 is 0% since we know that one children is girl and the question is "when A daughter answers..." not "when THE daughter answers...", which means that both are girls

>>12295194
shit i laughed

>>12297385
Maybe you're right. Walk me through it if you feel like being nice:
Girl only household:
G1 answers first, OR
G2 answers first.
Boy-girl household:
G answers.

It seems to me there's more of a chance that a girl answers the door on a girl only household. Where am I making a mistake?

>>12297474
Why didn't you include a scenario for a boy-boy household?

it should be 99.999999%

YES!

>>12297496
Cuz a daughter opens the door and there's only two children
Is this the setup for a joke

>>12295152
FBFP OP BTFO

>>12297262
>https://pastebin.com/YxYMzVY3
Your code has a critical flaw in the logic, I'll let you figure it out. What a waste of time to answer a 7th grade probability problem.

>>12297296
A girl answers the door, so you have eliminated both cases where a boy answers the door first. Now you have 2 possibilities:

>girl, then boy
>girl, then girl

Since you know girl answers first, your options are:

>then boy
>then girl

50% chance boy, 50% chance girl.

>>12297635
Please see >>12297474

Actually, the wording is a bit ambiguous. If you assume that at least one child is a girl, you get 1/3. If you drop this assumption you get 1/2 because you have to take into account the fact that you sampled the distribution when applying Bayes' theorem, in which case you'd get 1/2. I'm not sure which one is intended here.

>>12297675
The wording is not ambiguous. Read the fucking question.

>>12297706
I didn't really read it carefully. The "door" bit is critical because you're sampling the distribution, which you have to account for when applying Bayes.

>>12295844
GGG GB

>>12297733
Bayes has nothing to do with sampling. It seems you have no real knwoledge and are just applying buzzwords.

If the couple TOLD you that at least one of their children was female, (i) would be 2/3. If you go to their house and knocked on the door, (i) is 1/2.

>>12297750
>Just how do we know that "at least" one is a boy? One description of the problem states that we look into a window, see only one child and it is a boy. This sounds like the same assumption. However, this one is equivalent to "sampling" the distribution (i.e. removing one child from the urn, ascertaining that it is a boy, then replacing).

This is basically what you're doing, but replace "look into the window" with "knock on the door".

>>12297706
Please respond, senpai
>>12297675
>>12297760
https://en.wikipedia.org/wiki/Boy_or_Girl_paradox#Analysis_of_the_ambiguity
Ye

>>12297675
Why is it unreasonable to assume at least one child is a girl? both parts of the question tell you that a daughter answers the door, thus, to solve them, you are intended to use the knowledge that at least one of the children is a girl.

>>12297658
The question asks if a daughter answers a door what is the probability the other child is a boy. “Daughter” implies a designation of child type based on gender identification where as “boy” implies an actual birth gender. The possibilities are as follows:

Girl 1 -> Girl 2
Girl 2 -> Girl 1
Girl 1 -> Boy 1
Girl 1 identifies as boy -> Girl 2
Girl 2 identifies as boy -> Girl 1
Girl 1 identifies as boy -> Boy 1
Boy 1 -> Girl 1
Boy 1 -> Boy 2
Boy 1 who identifies as girl -> Boy 2
Boy 2 who identifies as girl -> Boy 1
Boy 1 who identifies as girl -> Girl 1

You can eliminate every possibility where boy answers or a girl who identifies as a boy answers, as these will be considered sons. You now have:

Girl 1 -> Girl 2
Girl 2 -> Girl 1
Girl 1 -> Boy 1
Boy 1 who identifies as girl -> Boy 2
Boy 2 who identifies as girl -> Boy 1
Boy 1 who identifies as girl -> Girl 1

3 possibilities girl, 3 possibilities boy. 50%.

>>12295142
Trick question. The answer to both is 1/2.
The questions don't ask what are the likelyhood that these outcomes occur. If that would be the case then the answers would be i) 1/4 and ii) 1/3 simply because for i) the problem space is
GG
GB
BG
BB
and for ii) the problem space is
GG
GB
BG
(Note we remove the BB part because we know that 1 child is a girl, so 2 boys will never happen).

HOWEVER!!!!! This is not what the question is asking here! It asks you specifically what is the probability the the NEXT PERSON who answers the doors is! It's super simple. It will always be 1/2. You can either have a boy or a girl answer the door.
so i) = 1/2 and ii) = 1/2 . Final answer

>>12297789
It's about how you came to know that one child is a girl. You come to know that one child is a girl by knocking on the door, and each child has an equal chance of opening the door. You don't know anything about the children's genders before you knock on the door. You want to find P(GB | g) where g is the probability of having a daughter answer when you knock, where P(BB) = P(GG) = 1/4 and P(GB) = 1/2.

>>12297825
>where "g" is
Fixed

>>12297799
You really went and typed all that, kek
Ok

>>12297825
Ah, I see what you mean, however, don't both questions present a conditional statement as indicated by the "if". I.e. they're asking, given g, find P(GB), however, you also know that given g, P(BB)=0, thus P(GB given g) = 1-P(GG given g), which is 1/3. I've never taken a class on probability so maybe I'm misunderstanding something, but that seems to be the case. Perhaps, instead, your argument is the right one, and mine works only for the second question where you know that P(BB)=0 before you knock, and thus would explain why there are 2 different questions

All your answers are wrong as it assumes that having a girl or boy are of equal likelihood.

https://en.m.wikipedia.org/wiki/Human_sex_ratio

>>12295152
*hits pipe*

>>12295225
I fucked your bitch you fat motherfucker
hey money

>>12297916
The methodology of solving this question is more important than the technical answer. If properly defining how one would use Bayes theorem here, you can trivially answer the question given any probabilities of likelihood of having a male child by just plugging numbers in

>>12297914
>From all families with two children, at least one of whom is a boy, a family is chosen at random. This would yield the answer of 1/3.
This is the case where you already know that at least one child is a girl.

>From all families with two children, one child is selected at random, and the sex of that child is specified to be a boy. This would yield an answer of 1/2.
This is the case in the OP. You select a child at random by knocking on the door, and its gender is specified.

>>12297837
You really have been arguing with people but been wrong this entire time. Better to be typing and be right than typing and be wrong IMO. Sorry, buddy.

>>12297978
Ah, I see, yes, you're right. I wouldn't say the problem is so much ambiguous as it is a good test of understanding the way you should approach the sampling, and the fact that I was getting the same result for both questions would be the hint that would suggest that this is something to pay attention to. Thanks!

>>12298089
You haven't posted a right answer, you wrote a wall of unfunny text

>>12295142
If you are asking the sex of the second child independent from the first the answer is 1/2.

If you are asking the chances of both children being girls it is 1/3.

>>12295152
FPBP OP BTFO

We had to do this in Genetics. A lot of people fail the question.

Part 1. A couple could have the following combinations
Boy 1st Girl 2nd , BB, GB, GG. Each combination is 1/4 chance because having a daughter or boy is 1/2 chance independently.

So since a girl answers the door we can eliminate BB. So out of the three remaining only GB, and BG lead to a boy and GG doesn't. So that is 2/3.

For part 2 we know the oldest is a daughter. That means the only combination can be GG, or GB. Since the daughter answers the door. We still can't eliminate GG or GB. However the tricky part is is the daughter the young or older daughter. And thus the GB scenario is dependent upon which daughter. If the youngest daughter answers there can be no boy possibility. So the chance of the oldest daughter answering is 1/2 and then the chance of either being youngest daughter or boy is each 1/2 so boy is 1/2 × 1/2 which is 1/4.

>>12297206
Age effects because if the youngest daughter answers then the other child has to be the oldest daughter no matter what. But if the oldest daughter answers then the next child can be a boy or girl.

This and the monty hall problem are guaranteed replies

Hmm I could be wrong on part 2 though. It may be that

A daughter answers is she ?
Girl old<-this1, girl young
Girl old, girl young <-this1
Girl old, boy young

So the chance of girl old answering is actually 2/3 and then it's 1/2 being GG or GB and that makes it 1/3.

>>12298482
See I don't quite understand why BG and GB are considered separately and GG isn't counted as "two" for this, since any of the girls could have answered the door (a girl answering the door is more likely if the house has only girls)
Pls explain

>>12298687
You might be right. I could be wrong on #1. The question is difficult to answer.

Who can answer the door?

BB *impossible if girl asnwer*
Old boy young boy
Old boy young boy

(BG)
Old boy young girl <-
Old girl<- young boy

(GG)
Old girl<- young girl
Old girl young girl<-

The arrows are all that can answer door.

So maybe it's 2/4 which is 1/2?

https://en.wikipedia.org/wiki/Boy_or_Girl_paradox
Well done everyone who said:
i 1/2
ii 1/2 or 1/3

Everyone else is retarded and should leave this board immediately

>>12298482
> So out of the three remaining only GB, and BG lead to a boy and GG doesn't
You can also eliminate BG because a boy didn't answer, or else, BG and GB are the same thing, so it's 1/2, right?

>>12298769
https://en.wikipedia.org/wiki/Boy_or_Girl_paradox#Second_question

Apparently it's a little bit fucky.
>>12298805
Oh hey. You got them backwards I think. And it's 2/3

>>12298818
Ye I fixed it here
>>12298769

>>12298805
>Everyone else is retarded and should leave this board immediately
irony, the post

>>12298988
Nice one

I) 2/3
II) 1/2

>>12299072
*II) 1/4..
Gonna agree with the age thing as outlined by >>12298482

>>12295142
1. 2/3
2. 1/3

I'm right. Google it or learn statistics

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

Everyone in this thread is wrong. The answer to i) is obviously 50%. Will not discuss i) as it is easy. The answer to ii) is 40%. Allow me to explain:

>>12295679
Came the closest, but the mistake is that he thinks there is an equal chance of a younger or older daughter answering the door first. There is not. The eldest child has a 2x chance of answering the door. <---- This sentence is integral to understanding the question, I would bold it if I could.

>>12295679
E= elder Y=younger g=girl b=boy

His math is Yg answering door= 0/1 chance of Eb. Eg answering door = 1/2 chance of Yb. Add numerator and denominator together and you get 1/3, the chance of Yb.

BUT if oldest is known as daughter, before you open the door there is a 3/4 chance of a girl answering it. After opening it, you now eliminate the boy opening it, and you have 2 chances of oldest girl opening and 1 chance of youngest girl opening. Like i said, oldest child has a 2x chance of opening door.

My math is Yg answering door = 0/1 chance of Eb. 1st instance of Ed =1/2 chance of Yb, 2nd instance of Ed = 1/2 chance of Yb. Add together all numerators/denominators, you have a 2/5 chance that the oldest daughter has a younger brother, 40%.

THE ELDEST CHILD HAS A 2X CHANCE OF ANSWERING THE DOOR. Its like Schrodinger's cat for younger child.

>>12295152
FPBP OP BTFO

>>12295152
FPBP OP BTFO

>>12299805
>Add together all numerators/denominators
That's not how it works retard. By your logic the oldest daughter is 4x as likely to answer the door.

>>12296036
>BG, younger answers door
how is this even an option if you know the oldest of the two children is a girl?

i think you should remove this as an option, so the three scenarios are:
GB, older answers door
GG, older answers door
GG, younger answers the door
and you're left with 33% change of the other child being a boy

>>12295142
i) 50%
ii) p= 0,5*1 + 0,5*0,5 = 0,75

graduated 2 years ago and havent used statistc since so idk

>>12295152
FPBP OP BTFO

>>12298195
>gets btfo
>can just say it’s “unfunny”
Fucking loser prove me wrong. Hint: you can’t.

So many brainlets in here

Who opens the door wouldn’t matter. It’s asking if male or female. There are 2 choices so it’s 50/50

>>12298805
>>12297837
There you go you degenerate low IQ. 50%. 50. 50. 1/2. You fucking lose. Happy new year!

Wow what a cringe thread, so many brainlets.

(i) is 50%
(ii) is 66.66%

Reasoning:
For I, this is trivial, the genders are equally likely and the children are probability wise independent. Therefore the second child is still 50/50 between girl/boy

For ii, there are two possibilities.
GG and GB
A girl answers the door and you don't know if that daughter is the oldest. There are 3 possible girls that answer, 2 of which are in the GG group, therefore P(GG)=2/3. It's as simple as that, there is a selective bias for GG that is why it isn't 50%.

>>12295152

>>12300580
>calling others cringe and brainlets
>didn't even read the problem

>>12300614
33.33% whatever faggot.

Your actual brainlets. Holy fucking shit how the fuck do you not see it’s 50/50? There are 2 choices. Male or female. 2 choices so it’s 50/50. How the fuck do you brainlets not get this?

>>12300744
What if the youngest sister answers the door instead of the oldest? What's the probability that an older brother is also the older sister?

>>12295142
Gender is fluid.

1) gender of second child completely independent of first child. 50/50
50 percent


2). is the person who answered the eldest?
>50% no -> the other child, the eldest, is a girl.
>50% yes -> the other child is 50/50 a boy or a girl

50 percent plus (50/2=25) percent = 75 percent

final answer

>>12300804
sorry 25 percent for part 2

>>12295152
FPBP OP BTFO

these replies are bearish

Such brainlets on biz

>>12295679
Please tell me it's a bait. It must be, right?

>>12295152
FPBP OP BTFO

1. 1/2
2. 1/3

proof: the 'sample space' of the second configuration is evenly distributed between:

Gg, G answers
Gg, g answers
Gb, G answers
Gb, b answers

conditioning on either G or g answering (you can't distinguish them), 1/3 of the sampled configurations are Gb and 2/3 are Gg.

if you dispute this then get off my board you Dragonchain bagholder

>>12302232
I misread part 1, part 1 is actually the same question as 2, except there's no extra step needed to coerce the two indistinguishable observations of younger or older girls to the same 'observed a girl'

>>12302269
which is to say, learning that the older sibling is a girl, or actually observing a girl, no matter which order you learn these facts in, conveys the same information and cannot update the balance of probabilities beyond the update that occurs when you first learn either.

>>12295142
y'all dumb as fuck, answer is...
i) 1/3 odds
g/g
g/b - b/g
b/b
ii) 1/2 odds
g/g
g/b

>>12295152
OP BTFO BIBLICALLY

There is an infinite/moving to 0 probability, since the other child could identify as any gender it wanted to.

>>12295152
FPBP OP BTFO

1. 66%
boy girl
girl boy
girl girl


boy is secluded

2. 50%

girl boy
girl girl

>>12304079
sorry firrst is 33%

There's a 50% chance the youngest opens. Then there's a 100% chance the other sibling is a girl.
Then there's a 50% chance the oldest child opens the door. There's a 50% chance the other child is a girl then.
Therefore it's a 0.5*0.5 = 0.25 chance of the other child being a boy

>>12295142
it's always 33%, a boy, a girl or gender fluid

>>12295152
FPBP OP BTFO

wtf there are so many retards here...
Every one is wrong by the way.
The real answer is no fucking idea.
Depends on their age and where they are.
Unless we do the average which I do not really know.
On average the chances of it being a boy are I guess 51-52%. More boys than girls are born but chinese literally murder their daughters, and boys have a lower chance of surviving their first years, on average around 10 yo there are like 102-105 boys for every 100 girls if I am not mistaken.
So 51-52% odds are going to be pretty close to reality.

>>12295152
FPBP OP BTFO

(i) 1/2
(ii) 1/3

for (ii) there are 3 independent variables with 50/50 distribution (X the sex of the child opening the door, Y the sex of the other child, Z = 1 if X is the eldest child, Z=2 if Y is the eldest)
so there are (without any further knowledge) 8 possibilities with each probability 1/8:
X=g or b, Y = g or b, Z = 1 or 2...
Now only look at the possibilites that satisfy the problem (i.e. gg1,gb1,gg2) and there you have 1/3.

>>12300499
That anon quoted the answers wrong, retard

>>12295152
FPBP OP BTFO