/sci/ - Science & Math

[Anonymous No.3267337]

[Anonymous No.3267350]

>>3267337
0%
Source: I flipped two coins. One of them was heads and the other wasn't, so they weren't both heads.

[Anonymous No.3267354]

1/2

[Anonymous No.3267360]

>>3267350

One is always heads. So get two coins, place one with heads up, and flip the other one.

[Anonymous No.3267367]

[Anonymous No.3267373]

0.333...

[Anonymous No.3267375]

[Anonymous No.3267381]

1/2

[Anonymous No.3267393]

what's the probability I give a shit?

[Anonymous No.3267399]

>>3267393

you posted so ... 50%

[Anonymous No.3267413]

>>3267375
25%.

[Jennie No.3267418]

all posibilities:

T T
T H
H T
H H

we ignore the top one because at least one is heads. The probability that they're both heads is 1 for 3.

[Anonymous No.3267419]

>>3267373

Actually this.

[Anonymous No.3267420]

1st heads, 2nd tails
1st heads, 2nd heads
1st tails, 2nd heads
1st tails, 2nd tails

The last one is excluded, meaning that out of 3 situations, one will produce 2 heads, resulting in a probability of 1/3.

[Anonymous No.3267421]

>>3267375
32/113

[Insinuates gODS No.3267426]

0.9999... = 1

[Anonymous No.3267429]

>>3267418

So TH and HT aren't the same?

If one of them is definitely heads, it would depend on if that meant one of them or specifically one of them. If the left or right is always heads, it's 50%. If the heads is random, then that's correct.

[Anonymous No.3267440]

>>3267429
This type of problem is retarded. It involves the fact that the answer is different if you say one coin is head or the first coin is head.

[Jennie No.3267446]

>>3267429

[Anonymous No.3267451]

1/3, not independent events, etc.

[Anonymous No.3267473]

P(H | H) = 0.5
P(T | H) = 0.5
P(H | T) = 0.5

Prove me wrong.

[H+ No.3267489]

Bitches cannot into Bayes Theorum

http://yudkowsky.net/rational/bayes

[Anonymous No.3267495]

Normally, the probability of flipping 2 coins and both landing on heads would be P(H and H) = 0.25. However, since one coin is said to be heads and you want the probability that both are heads, you can conclude that the probability of getting heads on the second toss GIVEN GIVEN GIVEN GIVEN GIVEN that the first coin is heads = 0.5.

Also, flipping 2 coins is an independent event, the previous poster is a retard.

[Anonymous No.3267502]

>>3267495
if OP had said the FIRST coin was heads, they would be independent events. OP did not.

[Anonymous No.3267505]

>>3267502
If you want the probability of two coins being heads, the first coin must be heads, idiot.

[Anonymous No.3267507]

>>3267505
5/10, I started replying.

[Anonymous No.3267510]

don't know, don't care

[Anonymous No.3267513]

FUCK THIS THREAD

OP I HOPE YOU SUFFOCATE TO DEATH YOU MOTHERFUCKER

[Anonymous No.3267519]

HH
HT
TH
TT

1 out of 4 possibilites. 25%.

thread/

[Insinuates gODS No.3267522]

New challenge: If you have two coins with the volume of a 1€ coin.

What's the chances of them ending up like this if you throw them up randomly, with random wind-resistance. No more information. Give your best answer.

[Anonymous No.3267525]

>>3267519 here
wow im retarded, dont include TT so 1/3

[Anonymous No.3267526]

>>3267519
one of them is not possible

[Anonymous No.3267549]

>>3267522
0.

[Anonymous No.3267556]

>>3267522

Too many variables to determine an actual answer.

[Insinuates gODS No.3267558]

>>3267549
Can you prove that? Where did you get that value from?

[Anonymous No.3267568]

>22
assuming "random" means any number, P!=2*∞*∞

[Anonymous No.3267569]

>>3267558
not enough information. It depends on how you throw the coins.

[Insinuates gODS No.3267579]

>>3267556
>>3267556
That's your best answer? pff. I thought /sci/ could do better.

>Protip: geometrical probability.
Try again.

[Anonymous No.3267593]

>>3267558
Yep. 0 is the answer because firstly because there are an infinite number of ways the two coins could contact, meaning that specific one is 1 in infinity, and secondly because there's too little information (random wind speed could be any speed from -infinity to infinity years.

[Anonymous No.3267597]

>>3267593
I don't know why I put years instead of a )

[Anonymous No.3267601]

Holy shit /sci/ i thought you guys were smart.

Flip 2 coins and write down what they are, don't write down TT. Then look at the number of HH you wrote down. It'll be about 1/2 everytime

[Jennie No.3267632]

>>3267601
are you retarded? have you even done this more than once?

[Anonymous No.3267642]

>>3267601
don't worry, the 1/3 is just a mathematical way of dealing with unobserved uncertainty. You'll actually never encounter a physical situation where you know that one of the coins is heads without knowing which one it is.
>UMAD MATHFAGS?

[Anonymous No.3267675]

>>3267601
nope.
my java is incredibly shitty and my C++ is non-existent, but if anyone wants to clear this up, that'd be awesome.

java.util.Random


//1 is HEADS, 0 is TAILS
public static void main(string args){
int iNoOfFlips=0;
int iTotalNoOfFlips=100;
int iNoOfHeads;
int iNoOfTails;
do{
bool bCoin1 =random.nextBoolean();
bool bCoin2 =random.nextBoolean();
if(bCoin1==0&bCoin2==0){
iNoOfFlips++;}
if(bCoin1==1&bCoin2==1){
iNoOfHeads++;
iNoOfFlips++;}
else{
iNoOfTails++;
iNoOfFlips++;}
while(iNoOfFlips<iTotalNoOfFlips);
System.out.print("there were ");
System.out.print(iNoOfHeads);
System.out.print(" situations in which the second coin was heads, and ");
System.out.print(iNoOfTails);
System.out.print(" instances in which this wasn't the case.");
}

[Anonymous No.3267683]

>>3267418

Actually only two

HT
HH

We know 1 is heads. You are assuming you can tell the difference between the coins. Even if you do assume their is a difference then still it's 1/2

[Jennie No.3267686]

>>3267683
The universe can tell the difference between the coins. Their wave functions aren't entangled, they're different coins.

[Anonymous No.3267732]

>>3267683
what about TH?
I'm currently downloading eclipse again to see if I can fix and compile my shitty code into something that gives you results.

[Anonymous No.3267738]

>>3267686
That sounds.... almost christian.

[Anonymous No.3267747]

hold on a minute

Flip the two coins at the same time. What's the chance you got one head or more? (75%). Now, what's the chance you got two heads? (25%) Meaning for every three situations in which At least one is heads, you get one situation in which there are two heads.

[Anonymous No.3267750]

sage

[Insinuates gODS No.3267756]

>>3267738
>obsessed religionisticism

[Anonymous No.3267764]

>>3267337
This is a statistical problem:
Given that one coin is head, whats the probability of the other coin being head. I'd use a tree diagram here. As we use the "Given that" term, this means that we only need to find the probability of a coin being head which is 50%.

[Anonymous No.3267776]

>>3267764
Nope. Given that has no significance beyond being a prequisite. see >>3267747
which I think should explain the solution for you. Working on a practical proof now.

[Anonymous No.3267782]

>>3267738

Not really, If you were to colour the T side of both coins a different colour you'd see that the chance is 1/3rd because you can tell which coin is which.

[Anonymous No.3267785]

>>3267776
No, it says in OP's picture, "Atleast one is heads", so it assumes for you already what one of your coins is head. Now all we need to find is the probability that the other is a head so that "both are heads". Therefore its a very straightfoward answer of 50%.

[mtp No.3267786]

L2probability

its p(H|H)
probability of heads GIVEN heads
so its fucking 1/2
stupid HS cunts

[Anonymous No.3267794]

>>3267786
Exactly what I meant, but most of these people havent learnt about the "given that" term in Statistics (Edexcel)

[mtp No.3267799]

>>3267794
personally im WJEC

but its funny how people think theyknow what theyre saying when clearly they dont have a clue ;s

[Anonymous No.3267801]

>>3267785
No. At least one is heads does not mean At least the first is heads. The chance of any individual coin being heads is 50%. The chance of any of two coins being heads is 75%.

[Anonymous No.3267807]

>>3267799
Yeah it was kinda annoying seeing how many people fail in their thoerys in this thread. Shows me how many people dont really listen in class or whatnot

[Anonymous No.3267810]

>>3267801
I dont disagree in your 75% there for 2 heads. However, it clearly states that the first IS a head, and ask for the chance for the 2nd to be head = 50%

[Anonymous No.3267817]

>>3267810
It only says AT LEAST that one of them is heads.

Which leaves 3 possibilities to be able to get

TH
HT
HH

Therefore it is 1/3rd

[Jennie No.3267818]

>>3267738
>>3267756
>>3267738
>>3267764
except you flip two coins, and the coins aren't the same coin. Even if you count the TH and HT as the same event, there are two different ways it can happen:

did it in secondlife (yea, secondlife. :| ), the box is doing the coin flips using random booleans. first number is HH, second number is HT, third number is probability of HH.


integer A=0;
integer B=0;
float headsheads=.000001;
float tailsheads=.000001;
integer run;
float division;

integer randBool()
{
return llRound(llFrand(1));
}

default
{

touch_start(integer total_number)
{
while(1)
{
A = randBool();
B = randBool();
if(A&&B)
{
headsheads++;
}
else if(A||B)
{
tailsheads++;
}
division = headsheads/(tailsheads+headsheads);
A= 0;
B= 0;
llSetText((string)headsheads + " HH and " + (string)tailsheads + " TH. " + (string)division, <1,1,1>,1);
}
}
}

/*
init
loop:
get random number
put into variable
get another random number
put into variable
if A and B
add HH
clear repeat
if A or B
add HT
clear repeat
if !A or B
clear repeat
set text
*/

I am a faggot.

[Anonymous No.3267822]

>>3267801
IT doesn't state the first is a head, it states one is a head. How on earth did you get that from "you flip two coins. At least one is heads"?

Also, I'm getting an error message that some of my integers may not have been initialised. What do?

[Anonymous No.3267825]

When the world is populated by these kind of retards than don't even know the most basic forms of probability and english language, no wonder the casinoes are running such a massivie profits.

Learn to sage so that these troll threads can die.

[Anonymous No.3267849]

>>3267818
the fuck is this, it looks interesting.
Also, I ran ten million iterations of the problem, look what I got.

[Anonymous No.3267856]

>>3267786
This.
P(H|H) = P(H and H) / P(H) = 0.25/0.5 = 0.5

[Anonymous No.3267860]

>>3267856
No. Look above you.

[Anonymous No.3267864]

>>3267817
Ah, I think this guy is correct

[Anonymous No.3267903]

>>3267849
import java.util.Random;
public class main {

//1(true) is HEADS, 0(false) is TAILS

public static void main(String[] args){
int iNoOfFlips=0;
int iTotalNoOfFlips=10000000;
//change this to change the number of times it runs the program. Flips in which neither variable are a head are not counted in this.

int iNoOfHeads=0;
int iNoOfTails=0;
//initialises all the variables we need

Random random = new Random();
//initialises a pseudorandom number generator called "random".

do{
boolean bCoin1 =random.nextBoolean();
boolean bCoin2 =random.nextBoolean();
//creates two booleans called bCoin 1 & 2, and assigns them a random value.

if(bCoin1==true&bCoin2==true)
{
iNoOfHeads++;
iNoOfFlips++;}
//if both the booleans are heads, this increases the number of heads then increases the number of flips recorded.

else{if(bCoin1==false&bCoin2==false||bCoin1==true&bCoin2==false){
iNoOfTails++;
iNoOfFlips++;
}//if the first is a tails and the second a heads, OR the first a heads and the second a tails, this increases the number of tails then increases the number of flips recorded.

}
}
while(iNoOfFlips<iTotalNoOfFlips);
//this runs the code within do{ and the bracket above while for as long as the number of flips performed is less than the total number of flips wanted.

System.out.print("there were ");
System.out.print(iNoOfHeads);
System.out.print(" situations in which the second coin was heads, and ");
System.out.print(iNoOfTails);
System.out.print(" instances in which this wasn't the case.");
//This prints to the console the results in a human readable format
}
}

[Anonymous No.3267905]

Heres the soloution

[Jennie No.3267921]

>>3267849
you made a mistake.

In your third test, you test if FALSE FALSE or FALSE TRUE, when it should be TRUE FALSE or FALSE TRUE.
Also, it's Second life. If you get into it, avoid the fags. 80% of second life is assholes and idiots.

[Anonymous No.3267929]

>>3267921
good point, changing now. This shouldn't actually make any difference, but I might as well change it.

[mtp !EKFQOBEsKo No.3267947]

>>3267903
else{if(bCoin1==false&bCoin2==false||bCoin1==true&bCoin2==false){
iNoOfTails++;
iNoOfFlips++;
}//if the first is a tails and the second a heads, OR the first a heads and the second a tails, this increases the number of tails then increases the number of flips recorded.

but thats just wrong

it adds a false false as true false
nice logic dude

now we know why your results were 1:3

now change the algorithm, make it right and then youll see 50:50

[mtp !EKFQOBEsKo No.3267954]

>>3267929
seriously? what the fuck am i reading?

[Anonymous No.3267979]

An important note to make here is that the two coins are indistinguishable in the context of this problem. Meaning, when you say "at least one is heads," it can mean either one. This affects the probability.

If the problem stated "You flip two coins. The first one came up heads. What is the probability that both are heads?" It would now be 1/2 because the two coins are distinguishable. You can now put the first coin aside and only look at the possible outcomes of coin 2. Even if the problem was "the dirtier coin came up heads" or "the coin of lesser value came up heads" this would still be the case since there is a way to distinguish between the two coins, therefore you can automatically cross of two of the four possible outcomes.

However, since the two coins are INdistinguishable, you must look at every possible outcome and only cross off the outcome in which both coins came up tails. Which is why, in this case, it is 1/3.

[Anonymous No.3267981]

>>3267954
see:
>>3267818

[Fix'd java No.3267994]

import java.util.Random;
public class main {

//1(true) is HEADS, 0(false) is TAILS

public static void main(String[] args){
int iNoOfFlips=0;
int iTotalNoOfFlips=1000000000;
//change this to change the number of times it runs the program. Flips in which neither variable are a head are not counted in this.

int iNoOfHeads=0;
int iNoOfTails=0;
//initialises all the variables we need

Random random = new Random();
//initialises a pseudorandom number generator called "random".

do{
boolean bCoin1 =random.nextBoolean();
boolean bCoin2 =random.nextBoolean();
//creates two booleans called bCoin 1 & 2, and assigns them a random value.

if(bCoin1==true&bCoin2==true)
{
iNoOfHeads++;
iNoOfFlips++;}
//if both the booleans are heads, this increases the number of heads then increases the number of flips recorded.

else{if(bCoin1==false&bCoin2==true||bCoin1==true&bCoin2==false){
iNoOfTails++;
iNoOfFlips++;
}//if the first is a tails and the second a heads, OR the first a heads and the second a tails, this increases the number of tails then increases the number of flips recorded.

}
}
while(iNoOfFlips<iTotalNoOfFlips);
//this runs the code within do{ and the bracket above while for as long as the number of flips performed is less than the total number of flips wanted.

System.out.print("there were ");
System.out.print(iNoOfHeads);
System.out.print(" situations in which the second coin was heads, and ");
System.out.print(iNoOfTails);
System.out.print(" instances in which this wasn't the case.");
//This prints to the console the results in a human readable format
}
}

[java No.3268005]

>>3267947
changed, ran a billion times
The chance of one of two coins being H is the same as the chance of both coins NOT being tails(which is <span class="math">1-0.5^{2}[/spoiler]) The chance of both of the coins being Heads(<span class="math">0.5^{2}[/spoiler]) over the chance of at least one being heads(0.25/0.75) is the proportion of tosses in which at least one heads is thrown in which the other is heads.

I know it seems utterly impossible. I thought it was too until this clicked.

[Anonymous No.3268012]

Fuck this thread already..

sage

[java No.3268015]

>>3268012
Fuck this thread (it's 1/2) or Fuck this thread (it's 1/3)
Both are retarded. One is uninformed as well.

[Anonymous No.3268016]

probs:
AA
AB
BA
BB

If at least one is heads than thar leaves 1/3 of a chance that both are heads.

This kinda reminds me of the monty hall problem
http://en.wikipedia.org/wiki/Monty_Hall_problem

[mtp !EKFQOBEsKo No.3268026]

http://www.mathgoodies.com/lessons/vol6/conditional.html
im sorry but maths doesnt lie. it is 1/2

and that simulation does not yield the desired result, because it accounts for both coins having random results, when in fact we are just flipping one coin since we have "set" the result of one throw to be heads. anyone saying otherwise ask any mathematician in your school. for fuck sake why am i raging in a troll thread?

[Anonymous No.3268039]

>>3268026
The problem is that you lack the reading skills needed for this assignment.

You don't understand the question and you are probably trolling so you could just stop already.

It's 1/3 the math doesn't
Try it out yourself.
Or ask your older brother who knows math and also knows how to read.

[java No.3268059]

>>3268026
FGS
The simulation mimics OP's post entirely.First, it flips two coins randomly. It then ignores the situations in which there are no heads (as OP does) leaving us with Two coins which we have flipped, at least one of which being a Heads. As OP did.
You clearly lack the knowledge required to talk about probability if you are still repeating something that only applies if we assume TH and HT are the same situation.

[Anonymous No.3268075]

>>3268026
Hey EK, I didn't know you were that retarded. Kinda fapped to you this morning, but now I feel even dirty about it.

[Anonymous No.3268099]

>>3268026
Sure is troll in here.
You flip two coins, not one coin. That's why it's 1/3 If you think otherwise then you're retarded and don't belong in any math position other than "basic college math student"

[mtp !EKFQOBEsKo No.3268100]

>i has thrown a coin
>got heads
>here, you throw another coin
>what is the probability that you will also get heads, given that i has heads????????????

and im outta 'ere

[java No.3268106]

>>3268100
Explain what went wrong here
>>3268059
also, accepting you're incorrect with probably stop us from assuming you're an arrogant dick.

[Anonymous No.3268119]

>>3268100

Yes you should as that just demostrated how retarded you are. You should try to learn basic logic and english before you come back. Preferably wait couple of years to finish the high school.

That is in no way similar to the OP exept that both feature coins
Hint: If you can't make it work using the OP's wording you are doing it wrong.

3/10 because i posted twice.

sage

[Anonymous No.3268124]

>>3268100

It says "At least one of them is heads".

It doesn't say which one, the first one or the second one.

Now you understand?

[Anonymous No.3268131]

you could flip tails then heads
you could flip heads then tails
you could flip heads then heads

obv makes it 1/2 you dumb cunts

[java No.3268145]

>>3268131
I disagreed with you, like, 333 million times.

[HTML No.3268162]

>>3268145
>java

pfft

[Anonymous No.3268166]

>anon asks troll question
>85 responses

It's 50% probability.

[java No.3268169]

>>3268162
It's my name 'cos I used it. I agree it's bloated, and I'm in the process of learning the C++
>>3268166
nope. see my posts.

[Anonymous No.3268177]

>>3267642
>>3267642
>>3267642
>>3267642
>>3267642
>>3267642
>>3267642
>You'll actually never encounter a physical situation where you know that one of the coins is heads without knowing which one it is.

[Anonymous No.3268236]

>>3268177

How about if you set
a coin with one side heads and one side tails and
a double-head sided coin
both faced heads up
mix them around
and then flip them simultaneously?

That way you know at least one of the coins will be heads, but you don't know which one. Therefore the probability is 1/2.

[java No.3268251]

>>3268236
nope, because a coin that has a probability of 1 has no relevance, and the whole point is that you're working it out from a probability of 0.75 not 1.

[Anonymous No.3268291]

[Insinuates gODS No.3268305]

>>3268291
This is some fine math indeed.

[Anonymous No.3268322]

>>3268291

[Anonymous No.3268332]

>>3268291

Fucking flood detection

[Anonymous No.3268337]

>>3268291

And that's it

[Anonymous No.3268345]

>>3268177
Dark room.
You have bag on your head.
You hear someone's voice: 'I'm going to flip two coins until at least one of them is heads. Then you have to tell if the other is heads. If you win 20 times - you go home. If you lose 15 times - you're dead.'

Yes, you've guessed correctly. The misterious coin killer is striking again. Another /sci/ resident is going to doie tonight.

[java No.3268357]

>>3268337
Thanks. Helps to have book learning on side.

[EK !EKFQOBUFnQ No.3268365]

this thread again...
im probably late, but worded like that the answer is 1/3.
this kind of thread usually decends into 1/3 vs 50% arguments. but the 'thirders' are right in this case.
i think i even have an image for it...

[java No.3268383]

>>3268365
>mfw I agree with EK on something

[Anonymous No.3268386]

>>3268365

[Anonymous No.3268391]

HH
TH
HT
TT

25%


for at least 1 is head

HT
TH
HH

33%

[Anonymous No.3268415]

>>3268365
Nobody cares which is first or second. It is either a heads and heads or heads and tails. Changing the words doesn't change the outcome; it either is or isn't.

It's 50%

[Anonymous No.3268422]

>>3268365
I'm back......back to fap to WK, that is.

[Jennie No.3268424]

>>3268415
>>3268415
by doing it this way, you're only really flipping one coin. The problem calls for two coins, so you NEED to use the two coin model.

[Anonymous No.3268426]

>>3268415


Refer to

>>3268322
>>3268332
>>3268337

[Anonymous No.3268431]

>>3268365
I'm back......back to fap to EK, that is.

[Anonymous No.3268430]

>>3268391

I c wat u did thar.

[java No.3268438]

>>3268415
*sigh*
no, there are four possibilities

 A | B
_______
H | H
H | T
T | H
T | T

[EK !EKFQOBUFnQ No.3268448]

>>3268415
coins flip independently.
1 heads and 1 tails is twice as likely than 2 heads is.
(because there are 2 combinations of 1 heads 1 tails, only 1 combination of 2 heads)

[Anonymous No.3268456]

>>3268415
changing the words changes the rules and we all have to work within the rules, brosive

[Anonymous No.3268475]

magic coins that when flipped together will never both land on tails. leaving 3 possible outcomes, 1 of which is both heads. 1/3

[java No.3268481]

>>3268475
TT scenarios are just ignored, because they aren't relevant. Also, I like your image name.

[Anonymous No.3268552]

What happens if both coins land on edge?

[java No.3268558]

>>3268552
They don't get counted because there isn't at least one head.

[EK !EKFQOBUFnQ No.3268571]

>>3268552
a coin flipped properly (as in, it tumbles) cant possibly land on its edge.

[Anonymous No.3268572]

>>3268552
Time implodes.

[None !/oddSpacew No.3268877]

why did this suddenly stop?