[ 3 / biz / cgl / ck / diy / fa / ic / jp / lit / sci / vr / vt ] [ index / top / reports ] [ become a patron ] [ status ]
2023-11: Warosu is now out of extended maintenance.

/sci/ - Science & Math

View post   
File: 49 KB, 238x203, coins.png [View same] [iqdb] [saucenao] [google]
5583271 No.5583271 [Reply] [Original]

>> No.5583276

obviously 50%

/thread

>> No.5583280

Flipping coins are physically independent so the chance is 0.5

>> No.5583283

>>5583276
>/thread
Sorry buddy, there hasn't been the required shitstorm yet.

>> No.5583284 [DELETED] 
File: 157 KB, 1373x1122, heads_and_tails.jpg [View same] [iqdb] [saucenao] [google]
5583284

>>5583271
>oh_look_its_this_thread_again.

>> No.5583285

>>5583284
>infantile cartoon

>> No.5583289

>>5583284
The question is different

>> No.5583291 [DELETED] 
File: 62 KB, 400x505, 1324238910061.jpg [View same] [iqdb] [saucenao] [google]
5583291

>>5583285

>> No.5583292

>>5583276
>>5583280
http://en.wikipedia.org/wiki/Boy_or_Girl_paradox

>> No.5583293

>>5583289

How is the question different? That's exactly what it's asking.

>> No.5583296

>>5583293
one says "at least one is heads" the other says "one is heads"

so chance other is head is zero

>> No.5583301 [DELETED] 
File: 221 KB, 435x355, 13635748.png [View same] [iqdb] [saucenao] [google]
5583301

>>5583289
>The question is different
so, changing 'at least one coin is heads' to 'one coin is heads'
well, technically if ONE coin is heads, then the other isn't. otherwise TWO coins would be heads

so, 0% chance

>> No.5583302

>>5583296
are you retarded

>> No.5583304 [DELETED] 
File: 28 KB, 402x602, 1351879649003.jpg [View same] [iqdb] [saucenao] [google]
5583304

>>5583296
YEEAH!!

>> No.5583309

>>5583302
why yes. yes i am.

>> No.5583310

>>5583301
You're saying that if I get two heads I did not get one?

>> No.5583312

>>5583310
do you have one leg?

>> No.5583315

>>5583312
Yes I do.
It's right next to my other one.

>> No.5583324

>>5583319
nope

http://en.wikipedia.org/wiki/Boy_or_Girl_paradox

>> No.5583320

>>5583315
HA HA CRIPPLE!

>> No.5583318 [DELETED] 
File: 46 KB, 473x596, PGAmr.jpg [View same] [iqdb] [saucenao] [google]
5583318

>>5583310
no, you didnt get ONE, you got TWO

and TWO is a totally different number than ONE

>> No.5583319

Because they are independent events, the event of A = heads does not affect the chance that B = heads.

If the coin and toss are fair, and heads = .5, heads compliment = .5 are the only two outcomes, given that A = heads, the probability that B = heads = .5

>> No.5583323

>>5583271
Didn't feel the 2nd sentence was important enough to head. The answer is 25%

>> No.5583325

>>5583318
There is a difference between "one" and "only one".

>> No.5583328 [DELETED] 
File: 17 KB, 300x247, 1338237059001.jpg [View same] [iqdb] [saucenao] [google]
5583328

>>5583315
>It's right next to my other one.
hahah!!

>> No.5583333

>>5583319
who said A was heads? or indeed B

there are four possible outcomes with equal likelyhood

HH
HT
TH
TT

the TT has been discounted by the question, so HH is 1/3

>> No.5583341

>>5583325
so i have this science book, from the 80s, and it says the solar system has nine planets

and i thought. COOL THERE ARE AT LEAST NINE PLANETS

>> No.5583342 [DELETED] 
File: 157 KB, 268x355, davd_bowie_meth_NEO.png [View same] [iqdb] [saucenao] [google]
5583342

>>5583325
well yeh, but if someone says 'i have one eye' then you presume they lost the other one
if someone says 'i have one eye'
and they still have the other one, then you call them a fucking liar, for being a confusing dumbass!
otherwise they'd never say that, unless to be confusing.

>> No.5583347

>>5583342
This is math though.
Precise language is to be expected.

>> No.5583354

If exactly one coin came up heads, then it isn't even a question. So that's obviously not what it's asking.

>> No.5583355

what's that coin OP is it a victorian canadian quarter?

>> No.5583356
File: 81 KB, 311x311, You-must-be-new-here.jpg [View same] [iqdb] [saucenao] [google]
5583356

>>5583354
>never heard of troll thread

>> No.5583361

dont you have mandatory statistics and probability classes in usa?...
if you are looking for the probability of two events happening together, you multiply their probabilities.
ex: chance of rolling a 1 and a 6 = 1/6 * 1/6 = 1/36
if you are looking for the probability of either events happening, you add them.
ex: chance of rolling either a 1 or a 6 = 1/6 + 1/6 = 2/6

>> No.5583366

>>5583361

if you think the answer is 25% you are literally retarded

>> No.5583371

.5 x .5 = .25

The possibilities are

HH
HT
TH
TT

so 25%

>> No.5583380

>>5583371

If one of the coins came up heads, there's a 25% chance that both coins came up tails? Hoo boy

>> No.5583394

>>5583371
TT has been ruled out so 1/3

>> No.5583409

The chances are about 33.34%

So conflipping is basically a game of luck.

>> No.5583416

>>5583394
So has TH lol.

One is already heads so it's just a simple flip of one coin to be tails or heads.

>> No.5583417

>>5583409

>So conflipping is basically a game of luck.

my cunt is bleeding

>> No.5583423

>>5583416

TH has not been eliminated. If a person flips two coins, the first comes up tails, and the second comes up heads, it is accurate for them to tell you that at least one of them came up heads. Remember, in this scenario, both coins have already been flipped.

>> No.5583429

>>5583416
Where does OP say the first coin is the head?

>> No.5583430

>>5583416
Nope

google boy girl paradox

>> No.5583432

gee bill, how come you mom lets you have two heads

>> No.5583479

0% as the picture shows or if you see "[only] one coin is heads" as the final outcome.
25% before either coin is flipped.
33.333...% if you read "[at least] one coin is heads" but aren't seeing the coins.
50% if you look and see "one coin is heads" while the other is still undetermined.
/thread
Everyone else is stupid and/or trolling.

>> No.5583499

50/50 Both probabilities are independent of one another.

>> No.5584005

I like how some people think that the events
"Two flips turned out heads" and
"At least one flip turned out heads"
are independent events, and use that to argue a 50% chance.
What dumbasses.

>> No.5584123

Naw dumbasses you square that because there is 2
(1/2)2 = 2/4 = 1/3
and cuz there is 1 outcome for in that is head and 2 outcome for other that is either hear or tail
2+1 = 3
so theres like a 0.1111 chance or some shit
which aint right

>> No.5584140

50%

>> No.5584157

It depends on how you know that one coin is heads

>> No.5584170

0%

>> No.5584278

http://en.wikipedia.org/wiki/Bayes%27_theorem

>> No.5584294

How is HT different from TH? Fucking morons.

>> No.5584330

0%. Coins don't just turn into heads. Unless they released a new transformers toy.

>> No.5584357

>>5583302
No he is right.

If you have two coins, and 1 of them is heads, the other must be tails.

If they were both heads, he would have had to say 2 of them are heads, not "one of them are heads"

>> No.5584362

>>5583310
That would be deliberately misleading.

You wouldn't tell someone that you had one leg.
Or if you have two kids, you wouldn't tell someone that you had one.

>> No.5584597

>>5583284
But that's wrong...
the only relevant cases are the first 2... do i need to explain why?

>> No.5584599

>>5584597
yes, so that we can correct you.

>> No.5584604

Full explanation of this classic problem:
youtu.be/dOicHifW0sQ

>> No.5584617

>>5584357
It's saying you know one of them is heads, not "there is only one coin flipped to heads."

In which case, one of them is heads, so the other coin has a 50% chance to be heads.

>> No.5584648

It's threads like these that have me more and more convinced that the field of probability is pseudomathematics.

>> No.5584655

>>5583301
Stop pretending to be a youtube girl.

>> No.5584669

Never have I seen such niggerism in this thread.

You faggots need to know your probability rules:

AND is multiplication.

OR is addition.

The question states "What is the chance both coins are heads?" You can rewrite this question as "What is the chance that both coin A AND coin B are heads?"

Coin A = 1/2 to get heads.
Coin B = 1/2 to get heads.

1/2 * 1/2 = 1/4

There is a 1/4 chance that both coins are heads. Faggots.

>> No.5584670

>>5584669
>canot into conditional probability

>> No.5584681

>>5584669
>i just learned high school probability, but not yet conditional probability

>> No.5584699

This question is so retarded, I answered in like a month ago. Using empirical evidence.

I flipped two coins like 200 times.
Two heads would come up 32% of the time (obviously would move towards 33.3... %)

>> No.5584719

Who wants to be a millionaire, 33%, etc.

>> No.5584751

>>5583380
this one. it's 50% because the first head is predetermined.

it's either HT or HH

>> No.5584756

>>5584751
why do you think the *first* coin is given?

>> No.5584757

>>5583423
>>5583429

The first coin is always heads - it says so in the picture. am i being trolled, in /sci/?

>> No.5584760

>>5584757
>it says so in picture
no, it says "one coin is heads". so we could have HT or TH (or indeed HH, unless you think "one" means "exactly one")

>> No.5584762

>>5584756
>>5584760

I'm sorry guys, I could've swear it said "first coin". My bad.

>> No.5584764

>>5584762
>apology
>4chan
what's going on?

>> No.5584783

>>5584764
Welcome to a scientific board Anon.

>> No.5584788

I decided to test this in scheme. I got 50%.

(define hh 0)

(define th 0)

(define (buildl x) (if (< x 0) () (cons (cons (random 2) (random 2)) (buildl (- x 1)))))

(map (lambda (a) (cond
((and (= (car a) 1) (= (cdr a) 1)) (set! hh (+ hh 1)))
((or (and (= (car a) 1) (= (cdr a) 0)) (and (= (car a) 0) (= (cdr a) 1))) (set! th (+ th 1)))
(else ())))
(buildl 10000))

Pretty simple. Buildl builds a list of pairs with values 1 or 0. Then a function that updates two counters is mapped to the list.

If I made a mistake, let me know.

>> No.5584791

>>5584788

Oh wait never mind. I'm an tired and an idiot. It's 1/3.

>> No.5584807

You flip two coins:
HH
HT
TH
TT
1. You somehow know that at least one of the coins is heads:
HH
HT
TH
So 1/3.
or
2. You pick the first coin and it is heads:
HH
HT
So 1/2.

It all depends on how you phrase the question. "One" coin is a very ambiguous way to do so.

>> No.5584828

>>5584783

Shut the fuck up you fucking cunt

>> No.5584845
File: 6 KB, 344x240, 1350679321459.jpg [View same] [iqdb] [saucenao] [google]
5584845

Answer: 25%

The second outcome depends on the first.

Even though it says the first is heads, its probability was 0.5, and the second is still 0.5.

0.5 * 0.5 = 0.25

>> No.5584846

>>5584828
Is not to late in the UK you bloody bastard?