How smart is Sup Forums?

How smart is Sup Forums?

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courses.cs.washington.edu/courses/cse312/11wi/slides/04cprob.pdf
twitter.com/NSFWRedditGif

op is a bitch

checked

100%

if it's given that at least one landed heads, it'd be 1/2 chance for the other to land on heads.

Faggot.

1/4

50%

Read the question again, retard.

Also wrong.

2 coins heads = 1/4
1 coin heads = 1/2
One is guaranteed to be heads, 75% because 3/4

1/4 is correct.

1/3
HH
TH
HT
TT
TT is impossible so you are left with 3 combinations. You want 1 of these 3 combinations, hence, 1/3.

Incorrect. Read the question again.

2/3

CORRECT

1/3

Everyone else is fucking dumb.

1st flip heads 2nd heads
1st heads 2nd tails
1st tails 2nd heads
1/3

Fuck euros.

Shit coins for shit people. Pesetas for life!

...one billion?

Well, since it's given that one of them landed on heads and we need to figure out the chance of them both landing on heads, we only need to worry about the second coin. The second coin could either land on heads or tails, likely with an equal chance of the two. This would be a 1 in 2 or 1/2 or 50% chance of the second coin landing on heads. Again, we know the first coin is already heads so that leaves us with our final answer of 50%.

1/3
Just take two coins and try out all 3 possibilities where at least one is heads

1/3

50%

That's actually wrong because it doesn't take into consideration the coin that already landed on heads. You are counting the same data twice which is why you end up with 1/3 instead of 1/2.

>we only need to worry about the second coin

>implying the first coin landed heads.

This is why you're retarded. EITHER coin could be the heads coin. There are 3 equally likely ways to get at least 1 heads coin:
HH
HT
TH

HH is 1 of those 3

1 of 3

1/3

correct

trips checked it's one billion

this

>That's actually wrong because it doesn't take into consideration the coin that already landed on heads.

Yes it does, you stupid nigger. Stay in school.
1/3

doubles sealed it

>1 billion /thread

That's a retarded trick question. It doesn't even fucking make sense, I already got heads dumbass you never said I had to have an exact order. 2/10 u tried too hard

guys its one billion

>Basic conditional probability question
>trick question

You really are a fucking retarded nigger.

>what are the chances?
50/50 every single fucking flip. This is called RANDOM chance you dumb fucks, the odds never change.

Wow you are retarded

Alright.
Say you flip a coin. It lands heads. Put it on the table and ignore it, it doesnt matter. You now have to flip a coin, which if heads will fulfill the condition, and if tails will not. You have a 50% chance of getting heads on the second coin flip, so the answer is 50%. THE FIRST COINS DOES NOT MATTER. Op, as always, is wrong.

trolls say 1/3
correct is 1/2

/thread

Smartest in thread.

Except that isn't the scenario here. You don't have a coin already on heads. It's 1/3

Also smart. You can understand basic math.

>who the fuck are those!!!?

>unintuitive things never happen in math
>what are bijections from the plane to the line
>what is banach-tarski paradox
>what is equivalence between axiom of choice and well ordering principle
Stay mad, kid

At least one is guaranteed to always land heads. So the only question is if the other coin lands heads or tails. Two possibilities. 50/50

It’s fucking 50%.

There's not enough information given for only a single correct answer. There are three possible answers depending on how the person who flipped the coin resolved "given that at least one of them landed heads". If TT came up and they resolved it by reflipping both coins, then the answer is 1/3. If TT came up and they chose to just manually make one of the coins heads then the answer is 1/4 because TT always loses. If TT came up and they changed both coins manually to heads then the answer is 1/2 because TT always wins along with HH.

it is 1 in 3, 1 is already heads, so the other can either be heads, tails or land on it's side....

>Except that isn't the scenario here. You don't have a coin already on heads. It's 1/3
'What is the probability that they both landed heads given that AT LEAST ONE OF THEM LANDED HEADS'
the exact words of the question.

Which side though?

Also a acceptable answer.

9001%

That's a different scenario, nigger. You're fixing a specific coin. In OP question, the first coin could be tails.

In your scenario, you can only get HH or HT.

In OP scenario, you can get HH or HT or TH.
This is because for a 2-coin flip, there are 4 equally probable outcomes possible, (HH, HT, TH, TT) and if at least 1 coin landed heads, then only TT is no longer possible, leaving 3.

1/2 for your scenario
1/3 for OP question.

there is only 1 "side" to a circular coin

read OP pic again you moron

ITT: Faggot takes Psych 101 and decides to show off on the internet

Trips is correct. University of Washington confirms answer is 1/3

Source:
courses.cs.washington.edu/courses/cse312/11wi/slides/04cprob.pdf

1/3

This is ambiguously worded, and therefore doesn't have one correct answer, it has two potentially correct answers.

Assuming the first coin landing on heads is relevant to the answer, it's one in three. Assuming the first coin isn't relevant to the answer, it's one in four.

He's right you dumb cunt. There are 3 ways to get at least 1 heads coin and they're all equally likely.

You're wrong twice. Congratz, you're dumber than the 50% retards.

Let me just tell you why it is 1/2 in this scenario.

Because you have set a condition that one will always be heads. So that is a guarantee. Thusly only 1 coin exists which has a probable solution of Tails or Heads.

Thusly 50% chance.

No if's or but's, you created the condition that one is always heads.

Like i have said,
Is a perfectly acceptable answer, and your image even proves it by showing both questions side by side. The question is too ambiguous.

Eg-fucking-zactly.

No you fucking moron. I suggest you buy yourself a dictionary because you clearly don't understand the definitions of simple English words.
It said probability, not not possibility.
Plus that faggot isn't accounting that the coin can land on it's side.
that faggot, and you, if you aren't same fagging are trying to over complicate a simple mathematical riddle, yet don't even understand basic English.

Scenario A. Flip coin 1. If it lands tails then flip 2 MUST land heads.

Scenario B. Flip coin 1. If it lands heads then flip 2 can land either heads or tails. Does not matter.

Three ways to get to the right answer. 1/3

Let's try this bet at my shady casino where I'm the dealer and you don't see the coins until the end then. I will be completely fair if HH, HT, or TH come up. But how I resolve TT is left hidden from you depending on how you bet. If you bet on HH coming up, I will treat TT by manually flipping one of the coins so TT always loses. If you bet on HH not coming up, I will resolve TT by manually changing both coins so that they are HH and you lose. Since the problem gives me no directions about how I should resolve TT, I would be following the rules no matter which I do.

It's a trick question, the answer depends on how you understand the sentence.

If anything, this is probably part of some personality test to see how you interpret instructions.

>Thusly only 1 coin exists which has a probable solution of Tails or Heads.

Incorrect. BOTH coins are variable as EITHER coin can be tails, just not both tails simultaneously.

You are retarded because your nigger brain can't understand that there are 3 equally likely ways to get at least 1 heads coin for a 2-coin flip

HH is 1 of those 3

1/3

Complete and utter bullshit. What the fuck are you talking about?

>and your image even proves it by showing both questions side by side. The question is too ambiguous.

No, the image clearly shows that OP question is the 2nd one, and the answer to that is 1/3.

No, the fact you allready have a heads is predetermined, as it is a 'given'. You dont 'need to get' a heads, as you know you allready will due to how the question is worded.

4 possible out comes are:
>Heads, heads
>Tails, tails
>Heads, tails
>Tails, heads
OP eliminates tails tails by telling you at least 1 coin is going to be heads.
That leaves
>heads, tails
>tails, heads
>heads, heads
Exactly

>by manually flipping one of the coins so TT always loses.

You're fixing coins. OP question does not fix any coin.

1/3

That is where you are wrong, the fact is one will always be GUARANTEED to be heads, that is a 100% probability, which leaves only 1 coin that can be heads or tails, 50% probability.

Overall 50% chance.

Doesn't matter if it is the first coin that always shows heads or the 2nd, because it is guaranteed that one is heads constantly and that is a constant 100% probability for that situation.

He explains it better than i ever could.

>the fact is one will always be GUARANTEED to be heads

Wrong. Either coin could be tails just not both simultaneously. Again, you fail with basic conditional probability. Here, I drew you a Venn diagram with bonus Bayes' theorem solution.

Stay in school.

1/3

How am I fixing coins if I reflip one of them in the event of TT? The problem gives me no directions about how to handle when TT comes up. If the problem said "Given that at least one of them landed heads, and if they didn't, then both coins were reflipped repeatedly until this were true," then the odds are 1/3. Since no specifics were given how to resolve TT, then all are correct.

Yo, retard.

Answer this question.

Protip: It's 1/3

An easier way I could explain it is this.

Flip a coin, it's either heads or tails, 50% chance, the last coin will be a head guaranteed so 100%.

Flip a coin, lands on heads that is a guaranteed 100% outcome because of the premise of the question, so the last coin has a 50% chance of a head.

Of course they will still try and say it is 1/3rd but they would be wrong.

Riddle me this, if one is tails what will the other be?

Exactly. Guaranteed head.

The answer is 1/3 either way.

For every 2-coin flip where you get at least 1 heads coin, you will get both heads 1 out of every 3 times.

That is different, because the scenario that one coin is always heads has been removed, so it will be 1/3 chance.

Read the question. See how it says 'given'? That means it is garunteed.

So the 1st coin could be heads and the 2nd coin heads
or
the 1st coin could be heads and the 2nd coin tails
or
the 1st coin could be tails and the 2nd coin heads

1/3

It doesn't say whether the first or second toss is the given heads result. You assumed that.

Its a different question. Thats called a strawman fallacy. I will again stress the importace of 'given'. You can even take it literally. I 'give' you a heads flipped coin, and you get to filp the other.

1/4. Theres only four ways it can end. Head/Head, Head/Tails, Tails/Tails, Tails/Head

That would be correct if you let nature take it's course, it would be 1/3.

But since the stipulation of the fact one coin will always be heads changes the rules, thusly forcing only 1 coin to be a probable tails or heads.

It is simple maths.

But these are fair coins so we know TT CAN happen. What did the dealer do when this happened? How did he resolve TT when it happened to guarantee one of them were heads? The problem gave no directions about how he had to resolve this. He could still meet the conditions of the original problem by making one of the coins heads manually. He could still meet the conditions by making both heads manually. He could still meet the conditions by reflipping both until TT no longer comes up. The odds are different depending on which method of resolving TT is chosen.

IT DOESNT MATTER WHICH ONE IS GIVEN. THATS LITTERALY LIKE SAYING 1+2 != 2+1 BECAUSE THEY ARE IN A DIFFERENT ORDER. OMFG.

This.
You're retarded.

If you flip two coins 100 times (whatever) then eliminate all the ones with tails (half) 50% of your result would be both.

Just because 1/4 of the time it happens does not account for the rest of the question. Learn to fucking read.

>because the scenario that one coin is always heads has been removed

You're confused. If I flip a coin and it lands heads, it wasn't guaranteed to always land heads, you fucking retard. It landed heads by chance. This seems to be where your problem lies.

You think that because at least 1 coin landed heads, then a specific coin was GUARANTEED to ALWAYS be HEADS

This simply is not true.

2 regular coins were flipped. All possible outcomes are:
HH
HT
TH
TT

At least 1 of the coins landed heads (was not guaranteed to ALWAYS land heads)

Only TT is eliminated from the probability space, leaving 3 equally probable outcomes, ALL satisfying the condition of having AT LEAST 1 heads coin

HH or HT or TH

All EQUALLY likely

1/3

That isn't the questio Asked tho

Doesn't matter. One coin will be heads no matter what. That's the same as saying if we flipped a coin with a 50/50 chance of heads or tails. One coin is fixed as ALWAYS heads

>Tails/Tails

wrong, one coin is always heads

Holy shit you're all stupid as fuck.

Stfu and check these digits

...

'GIVEN THAT'

The "given" refers to the condition. This is a basic conditional probability question.

In the question, the conditional is that "at least 1 coin" out of 2 landed heads. Could be either coin. Either coin could be tails, just not both at the same time.

1/3. I know it's counter-intuitive, user, but if you take some time to think about it, you'll eventually understand the answer is 1/3

But it is true, because the question has that stipulation (one is always heads) it is in the question itself.

Which dismisses probability affecting one coin.

It is simple logic, perhaps the best thing would have been to word the question better.

>one coin will always be heads

OP question does not say this. You're making assumptions.

>at least 1 coin landed heads
is not the same as
>one coin will always be heads

Work on your reading comprehension before working on your logic/math

1/3

P(HH)=0.25

p(TH)=p(HT)=0.5

p(HH|HT+HH)=0.25/(0.25+0.5)=1/3

Conditional probability folks

but one coin must be heads in order for 2 coins to be heads

so 50/50