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Typical Mathematics.

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Powerdrone
464 posts
Joined October 2009
Powerdrone

Emaal wrote:

Rantai wrote:

Ahh damn I had the right thinking... missed the fact that the Tuesday boy could be either and not just the first born >.<

Thanks for rekindling my love for maths.
You my man, are welcome.
Fuck. You.

Math is the worst thing I have ever done in my entire life.
Mismagius
9,268 posts
Joined July 2008
Mismagius

Powerdrone wrote:

Fuck. You.

Math is the worst thing I have ever done in my entire life.
I didn't expect that from someone with a Sho avatar.
Rantai
1,000 posts
Joined July 2010
Rantai

Powerdrone wrote:

Fuck. You.

Math is the worst thing I have ever done in my entire life.
:(

I always found English to be the most painful class to sit through, especially when it wants to start talking about old literature.
Lybydose
osu! Alumni
2,024 posts
Joined January 2009
Lybydose
But sho doesn't do math, he just spouts mathematical nonsense
Mismagius
9,268 posts
Joined July 2008
Mismagius

Lybydose wrote:

But sho doesn't do math, he just spouts mathematical nonsense
"Do the math." - Sho Minamimoto
:o
GladiOol
4,475 posts
Joined August 2008
GladiOol
I hate kids who are born on tuesdays, they only give fucking math problems.
NotShinta
1,021 posts
Joined September 2009
NotShinta
No.
Arusha Shuna
1,793 posts
Joined August 2009
Arusha Shuna

GladiOol wrote:

I hate kids who are born on tuesdays, they only give fucking math problems.
:(
Shellghost
543 posts
Joined March 2009
Shellghost

Emaal wrote:

But even the mathematics guy, that made this question, says that it's right, the result I have. Which I got from him.
Hay guise! I made a question involving math that has an undetermined number of variables, but i'm not going to collect the answers given to me by several other mathematicians whom i befriend/respect to reach an agreed answer, i'm just going to assume i'm right! xD
Shellghost
543 posts
Joined March 2009
Shellghost
Also, you adopted the second child.
Jarby
2,963 posts
Joined August 2008
Jarby
You don't have any boys because I castrated them both before you got a chance to respond to my answer.
TKiller
4,390 posts
Joined May 2009
TKiller

strager wrote:

Let's put it this way.

I have two coins. I have flipped both.

On Tuesday, I flipped one coin (coin A). It was heads.

What is the probability the other coin (coin B) was heads? (Coin B was flipped on any unspecified day (which could be Tuesday).
TKiller
4,390 posts
Joined May 2009
TKiller
I'd kill anyone who'd answer this with 13/27
dNextGen
4,689 posts
Joined May 2010
dNextGen
13/27
Lybydose
osu! Alumni
2,024 posts
Joined January 2009
Lybydose

TKiller wrote:

strager wrote:

Let's put it this way.

I have two coins. I have flipped both.

On Tuesday, I flipped one coin (coin A). It was heads.

What is the probability the other coin (coin B) was heads? (Coin B was flipped on any unspecified day (which could be Tuesday).
50%, because that's a different question.
TKiller
4,390 posts
Joined May 2009
TKiller

strager wrote:

How is it different exactly?
Lybydose
osu! Alumni
2,024 posts
Joined January 2009
Lybydose

TKiller wrote:

strager wrote:

How is it different exactly?
Let's assume the problem does not specify Tuesday.

There are four possible ways you could have 2 kids:

BB
GG
BG
GB

You might think "hey why does order matter?" The reason is because you have to account for the fact that there are 2 times as many BG pairs as there are BB or GG. (For reference, flip a coin twice. You have a 50% chance to get HT/TH and a 50% to get 2 of the same)

Now, the problem states that one of the kids is a boy. That eliminates GG from the 4 possibilities, leaving us with:

BB
BG
GB

In 33% of those cases, the other child is a boy, in the other 66% it's a girl. Therefore, the answer to this question (when Tuesday is removed) is 33%.

strager's question is different because he specified the first coin as heads. Had the original question specified the first child as a boy, we would only have two possibilities:

BG
BB

Leaving us with 50% of course, even with Tuesday in there.

Now, the specification of a date in the original problem (Tuesday) alters the probability because it removes more BG pairs than it does BB pairs. This is because a BB pair has two chances at hitting a Tuesday birth date, while a GB/BG pair only has one shot.
Xgor
Elite Mapper
2,534 posts
Joined April 2009
Xgor
As far I heard it's 51% that it is a boy and 49% that it's gonna be a girl so 51% would be a more correct answer.
Shinde
osu! Alumni
707 posts
Joined April 2009
Shinde
http://www.sciencenews.org/view/generic ... look_wrong

"Everything depends, he points out, on why I decided to tell you about the Tuesday-birthday-boy. If I specifically selected him because he was a boy born on Tuesday (and if I would have kept quiet had neither of my children qualified), then the 13/27 probability is correct. But if I randomly chose one of my two children to describe and then reported the child’s sex and birthday, and he just happened to be a boy born on Tuesday, then intuition prevails: The probability that the other child will be a boy will indeed be 1/2. The child’s sex and birthday are just information offered after the selection is made, which doesn’t affect the probability in the slightest."

The answer is whatever Emaal wants it to be, since the original post was very lacking, badly phrased, and provided no information on how the selection of the boy was approached. (Which makes all the difference.) I don't really feel like explaining this statement further as you can just read the above link which explains it in detail. Correct answers may include 1/3, 13/27, and 1/2.

You can't just say the correct answer is exlusively 13/27 though Emaal, because your first post doesn't permit you to. You didn't provide enough information to determine which rationale would be used to calculate the probability.

/thread

Go away.
NoHitter
osu! Alumni
3,785 posts
Joined June 2009
NoHitter
/alternative question

I have an aunt who has two children. One is male. What is the chance that the other is female?
Answer
0%. My aunt has two male children.
Shellghost
543 posts
Joined March 2009
Shellghost

NoHItter wrote:

/alternative question

I have an aunt who has two children. One is male. What is the chance that the other is female?
Answer
0%. My aunt has two male children.
I don't like this post very much.
Loginer
osu! Alumni
3,459 posts
Here since the beginning
Loginer
Ugh, here we go.

strager wrote:

How is it different exactly?
Relevance and order. Example:

Alice holds a coin in each hand. Either coin could be either golden or silver. She holds a gold coin with the heads side face-up in her left hand. What is the probability that the other hand contains a gold coin?
Here's a list of all possible combinations.

Go = Gold, heads. Gx = Gold, tails. So = Silver, heads. Sx = Silver, tails.
Go Go
Go Gx
Gx Go
Gx Gx

Go So
So Go
Go Sx
Sx Go

Gx So
So Gx
Gx Sx
Sx Gx

So So
So Sx
Sx So
Sx Sx
Since we know the left hand holds a gold coin with heads facing up, any combination that doesn't have "Go" on the left side is impossible. This gives us a probability of 1/2. Note that the way the coin is facing is considered a relevant detail in this example. Next:

Bob holds a coin in each hand. Either coin could be either golden or silver. Bob holds a gold coin with the heads side face-up in one hand. What is the probability that the other hand contains a gold coin?
And then the combinations.

Go Go
Go Gx
Gx Go
Gx Gx

Go So
So Go
Go Sx
Sx Go

Gx So
So Gx
Gx Sx
Sx Gx

So So
So Sx
Sx So
Sx Sx
Note that "Go" can be either the left or the right coin in this example; we don't know which coin is in which hand. The probability in this case would be 3/7. This example is a simplified version of the problem in the first post. Now look at this example:

Charlie holds a coin in each hand. Either coin could be either golden or silver. Bob holds a gold coin in his left hand. What is the probability that the other hand contains a gold coin? The previously mentioned coin has the heads side facing up.
And here are the combinations:

G G
G S
S G
S S
The important thing here is why the detail about the face-up side was given. In the first two examples, the coin in question was (presumably) picked out because of both its material and face-up side. In this example, it was picked out only because of its material, with its face-up side being an additional detail that won't affect probability for the next pick. As for your specific example, saying "the coin was flipped on any day" is not even a detail at all.

In short, probability is a faggot, and the puzzle is basically a more advanced version of the boy or girl paradox.
Natteke
6,538 posts
Joined August 2009
Natteke
why did I open this thread
maal
Topic Starter
maal
What is this I have woken up to.
IppE
IppE
:words:
xsrsbsns
1,936 posts
Joined July 2010
xsrsbsns
There's logic in OT?
Shinde
osu! Alumni
707 posts
Joined April 2009
Shinde
"I have two children. One is a boy, born on a Tuesday. What is the probability that I have two boys?"

The problem with 13/27 in this question is that by introducing Tuesday and an unrelated younger/older scheme, you cause probability overlap which results in the 13/27. Let me rephrase it.

"I have two children. The younger is a boy, born on a Tuesday. What is the probability that I have two boys?"

1/2

By stating the younger is a boy, this causes Tuesday to become irrelevant and eliminate the probability overlap that causes the false 13/27. You could bullcrap your way into arguing some other factor like the tallest/shortest even with this sentence and still and get a probability chart that shows 13/27. I could even make a grid with this sentence replacing youngest/oldest with shortest/tallest for the X-axis (or Y, whatever you wanted to use previously in your younger/older probability chart) and get 13/27. How does that make ANY sense? It isn't natural to introduce random factors just because you can. And it's the act of doing that that results in 13/27 anyways.

The fault in 13/27 explanations lie in the fact that the grid location where the Tuesdays intersect should be considered independent of each other, and are not in such examples.

The question wording just makes you analyze the wrong things. I revoke my earlier statement, 13/27 is false no matter how you look at it. (As is 1/3, but I never thought it was 1/3 with the original post's wording.)

I hope that suffices because I'm sleepy and don't feel like getting into more detail, or thinking.
Shellghost
543 posts
Joined March 2009
Shellghost
I thought it was quite clear the mention of Tuesday was irrelevant since the start of this thread.
Loginer
osu! Alumni
3,459 posts
Here since the beginning
Loginer
You know what, fuck it. I'm not having another one of these endless arguments.

[quote="http://en.wikipedia.org/wiki/Boy_or_Girl_paradox":e7e14]The paradox has frequently stimulated a great deal of controversy. Many people, including professors of mathematics, argued strongly for both sides with a great deal of confidence, sometimes showing disdain for those who took the opposing view.Both sides are right in their own way, end of story.
Shellghost
543 posts
Joined March 2009
Shellghost
"Mr. Smith has two children. At least one of them is a boy. What is the probability that both children are boys?"

How did he initially get 1/3 with this? It's already clearly stated that one child is a boy. The answer depends entirely on the sex of the second child.

[quote="http://en.wikipedia.org/wiki/Boy_or_Girl_paradox#Second_question":a1de2]A big misconception in this problem is that the outcomes of BG and GB are counted as two separate outcomes, when in reality, they are only one.The question only asks the number of boys. It doesn't ask about the birth order.
Shinde
osu! Alumni
707 posts
Joined April 2009
Shinde

Shellghost wrote:

"Mr. Smith has two children. At least one of them is a boy. What is the probability that both children are boys?"

How did he initially get 1/3 with this? It's already clearly stated that one child is a boy. The answer depends entirely on the sex of the second child.

[quote="http://en.wikipedia.org/wiki/Boy_or_Girl_paradox#Second_question":4cb90]A big misconception in this problem is that the outcomes of BG and GB are counted as two separate outcomes, when in reality, they are only one.The question only asks the number of boys. It doesn't ask about the birth order.
Because you can rule out the G G pair since 'At least one of them is a boy'

G G
B G
G B
B B

Thus you have three pairs where only 1 is a possible solution.

Edit: This is why probability charts are bad, as with 13/27.
Shellghost
543 posts
Joined March 2009
Shellghost

Shinde wrote:

G G
B G
G B
B B

Thus you have three pairs where only 1 is a possible solution.
I'll assume you're tired.
The order doesn't matter, read my quote again, only the end result of what genders are present is what the questions asks for.

It's more like this

One birth - The other birth

B - B
G - G

You already have one birth being a boy, that's one out of two boys required to have 100% boys.
If the other birth was a boy, that would make 100% of births resulting in boys.
If the other birth was a girl, that would make 50% of births resulting in boys.

50/100
1/2
Shinde
osu! Alumni
707 posts
Joined April 2009
Shinde
Yeah I am tired. I was trying to state the faults of looking only at probability charts with false logic instead of making sure you're actually analyzing the information correctly. In wording the 13/27 seems correct and you can add up the outcomes, but that isn't the case. The same with the above example and failing to count BG and GB as one due to the wording.

I blame English. It is the greatest paradox of all.
maal
Topic Starter
maal
Refer to the Monty Hall problem http://en.wikipedia.org/wiki/Monty_Hall_problem
Shellghost
543 posts
Joined March 2009
Shellghost
I'm not sure if you are referring us to the Monty Hall Problem in correlation with the Two Children problem or to start another mathematical discussion.
maal
Topic Starter
maal
The first problem. Not another discussion.
Shellghost
543 posts
Joined March 2009
Shellghost
The Two Children problem has two variables with which one is eliminated in the question.

The Monty Hall Problem has three variables with which one is eliminated depending on your answer, this then increases the likely hood of the third option.

Unless your point is to push the idea that the highly improbable 1/3 answer is correct by giving us a different problem which DOES have what would commonly be thought to be a highly improbable answer.

There is also no spoon.

Anything else?
maal
Topic Starter
maal
I'm just pointing out, that the problems are the same. It's a probability question. You can't answer those. You can never get 100% correct answer.

"You choose one door, with a goat behind it, let's say door C. The host now asks you if you want to take another door, let's say door B. However, meanwhile you have no idea where the car is (the other doors have goats), the show host knows where the car is. He could choose to ask you if you wanted to open the door with the car behind it, or not. But, he asks if you want to change door, to door B. Door B might have a goat or a car, the same for door A. Should you choose door A?"


That's the problem, you can't get 100% correct an answer.
Shellghost
543 posts
Joined March 2009
Shellghost
You can't get a 100% correct answer in the situations described in the problems, but when we are asked to provide the probability of the outcomes it's different.
Kitsunemimi
2,188 posts
Joined April 2009
Kitsunemimi
aaaAAAAUUGGHHHHH
Rantai
1,000 posts
Joined July 2010
Rantai
Sweet crap, a lot can happen in one sleep period :S
kiki1419
221 posts
Joined December 2009
kiki1419
I hate probability.... :(
But i love Algebra&Geometry! :)
arien666
6,290 posts
Joined May 2009
arien666

Rantai wrote:

Sweet crap, a lot can happen in one sleep period :S
So that's why math is the best subject on school<<<

/me runs
Shellghost
543 posts
Joined March 2009
Shellghost
Well... The important thing is that i'm right :3
IppE
IppE

kiki1419 wrote:

I hate probability....
But i love Algebra&Geometry!
^
wmfchris
osu! Alumni
5,072 posts
Joined March 2008
wmfchris

kiki1419 wrote:

I hate probability.... :(
But i love Algebra&Geometry! :)

yeah come on bros get some algebra or geometrical questions lol

oh btw Monty Hall problem is much clearer than the Boy girl paradox orz.
mm201
osu! Alumni
4,495 posts
Joined August 2008
mm201
This problem has nothing to do with math, but everything to do with our natural interpretation of the question's grammar.

Most people reading this question would interpret it as being equivalent to the question, "I have two children: Alex and Jamie. Alex is a boy born on Tuesday. What are the chances that Jamie is a boy." (Deliberately gender-ambiguous names. Assume they have no relation to the problem.) This gives us two independent random events, each with 50% probability, meaning the correct answer is 50%.

A pedantic douchewad, however, may choose to interpret the question as, "I have two children. At least one is a boy born on Tuesday. ..." Then Emaal's solution holds.

You could also interpret the question as "I have two children. EXACTLY one is a boy born on Tuesday. ..." which would have a different solution again.

NoHItter wrote:

/alternative question

I have an aunt who has two children. One is male. What is the chance that the other is female?
Answer
0%. My aunt has two male children.
Lilac
Elite Mapper
1,515 posts
Joined December 2008
Lilac
I love you, MetalMario.
Shellghost
543 posts
Joined March 2009
Shellghost
He basically just summed up what was discussed in this thread. :/
eru
2,885 posts
Joined November 2009
eru

GladiOol wrote:

I hate kids who are born on tuesdays, they only give fucking math problems.
Wojjan
806 posts
Joined August 2008
Wojjan
You already have a boy.

The probability of having two boys is now equal to the probability of getting a boy which is about 1/2?
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