/sci/ - Science & Math » Thread #13311837

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Anonymous Tue 22 Jun 22:40:31 2021 No.13311837 View Reply Original Report

Quoted By: >>13311992 >>13312012 >>13312041 >>13312047 >>13312175 >>13312870 >>13314453 >>13314810 >>13315528 >>13315626 >>13318807

There's a probability of 4/9 that A happens.
If A happens, there's a 5/9 probability of B happening.

What is the probability of B happening?

Anonymous

Anonymous Tue 22 Jun 2021 22:45:20 No.13311865 Report

Quoted By: >>13311878 >>13312018

20/81 =~1/4

Anonymous

Anonymous Tue 22 Jun 2021 22:48:35 No.13311878 Report

Quoted By: >>13311886

>>13311865
How did you do it?

Anonymous

Anonymous Tue 22 Jun 2021 22:51:21 No.13311886 Report

Quoted By: >>13311903

>>13311878
I assumed A was the event preceding B chronologically

Anonymous

Anonymous Tue 22 Jun 2021 22:55:48 No.13311903 Report

Quoted By:

>>13311886
What's the formula

Anonymous

Anonymous Tue 22 Jun 2021 23:21:11 No.13311992 Report

Quoted By:

>>13311837
What?
What about C and D? Shitty question because you don't explain everything.

Anonymous

Anonymous Tue 22 Jun 2021 23:26:02 No.13312012 Report

Quoted By: >>13312104

>>13311837
5/9, if A happens. If A doesn't happens, then we don't know the probability that B happens. So without knowing if A happens or not, we can't say what the probability of B happening is, only that it's at least (4/9)*(5/9), which is the event that A happens and B happens, which is a subset of the event that B happens.

Anonymous

Anonymous Tue 22 Jun 2021 23:26:21 No.13312013 Report

Quoted By: >>13312018 >>13312024 >>13315632

Is this bait? 4/9 • 5/9 = 24.7% of B happening.

Anonymous

Anonymous Tue 22 Jun 2021 23:27:09 No.13312018 Report

Quoted By: >>13312028

>>13312013
>>13311865
Wrong.

Anonymous

Anonymous Tue 22 Jun 2021 23:28:46 No.13312024 Report

Quoted By:

>>13312013
24.7% = 247/100 != 20/81

Anonymous

Anonymous Tue 22 Jun 2021 23:30:59 No.13312028 Report

Quoted By: >>13312033

>>13312018
Oh fuck off, you’re not really going appeal to semantics and say it’s 5/9, are you?

Anonymous

Anonymous Tue 22 Jun 2021 23:33:01 No.13312033 Report

Quoted By: >>13312063

>>13312028
No. Why would it be 5/9?

Anonymous

Anonymous Tue 22 Jun 2021 23:34:19 No.13312041 Report

Quoted By: >>13312045

>>13311837
>there's a 5/9 probability of B happening
>What is the probability of B happening?
5/9

Anonymous

Anonymous Tue 22 Jun 2021 23:35:19 No.13312045 Report

Quoted By: >>13312862

>>13312041
Wrong. You missed the first part of the sentence you're quoting.

Anonymous

Anonymous Tue 22 Jun 2021 23:36:42 No.13312047 Report

Quoted By: >>13312054 >>13315428

>>13311837
You forgot to state that B can only happen if A happens. Otherwise B could happen without A

Anonymous

Anonymous Tue 22 Jun 2021 23:39:52 No.13312052 Report

Quoted By: >>13312059 >>13312104

somewhere between 0.2469 and 0.8025

Anonymous

Anonymous Tue 22 Jun 2021 23:40:07 No.13312054 Report

Quoted By: >>13312065

>>13312047
You are repeating what was already said. Read the thread before posting.

Anonymous

Anonymous Tue 22 Jun 2021 23:41:20 No.13312059 Report

Quoted By:

>>13312052
Hah, you gave an upper bound as well. The most correct answer ITT

Anonymous

Anonymous Tue 22 Jun 2021 23:42:06 No.13312063 Report

Quoted By: >>13312078

>>13312033
You can argue on semantics that A has to happen first for the probability of B but that’s bullshit. They’re independent events.
If event A precedes the probability of event B happening you’d have to multiply P(A) and P(B). Unless, I’m looking at it wrong, and these are dependent on each other. Of that’s the case you need to do B/A • A giving you 55.6% probability of B happening

Anonymous

Anonymous Tue 22 Jun 2021 23:42:21 No.13312065 Report

Quoted By: >>13312078 >>13312090

>>13312054
20/81 ~ 0.2469 ~ 25%
where is the bait?

Anonymous

Anonymous Tue 22 Jun 2021 23:45:30 No.13312078 Report

Quoted By: >>13312118 >>13312886

>>13312063
>You can argue on semantics that A has to happen first for the probability of B
Can you?
>They’re independent events
You sure?
>If event A precedes the probability of event B happening you’d have to multiply P(A) and P(B)
That would get you P(A and B) which is not the same as P(B), and it only works if A and B are independent, which we are not given.
> that’s the case you need to do B/A • A giving you 55.6% probability of B happening
You sure bro?
>>13312065
20/81 is not the correct answer. Read the thread.

Anonymous

Anonymous Tue 22 Jun 2021 23:48:22 No.13312089 Report

Quoted By: >>13312104 >>13312113 >>13315711

I'm OP.

There's a 4/9 chance of team A qualifying for next round because of tournament rules. If team A qualifies for next round, there's a 5/9 chance that they play against team B and not team C or D because of tournament rules.
What is the probability of team A playing against team B?

Anonymous

Anonymous Tue 22 Jun 2021 23:48:47 No.13312090 Report

Quoted By: >>13312092

>>13312065
>where is the bait?
subtle

Anonymous

Anonymous Tue 22 Jun 2021 23:50:33 No.13312092 Report

Quoted By:

>>13312090
What?

Anonymous

Anonymous Tue 22 Jun 2021 23:52:38 No.13312104 Report

Quoted By: >>13312124

>>13312089
Dude, you already got your answer here
>>13312012
and here
>>13312052
Accept it and move on.

Anonymous

Anonymous Tue 22 Jun 2021 23:55:25 No.13312113 Report

Quoted By: >>13312124

>>13312089
If they don't qualify then they can't play team B so it has to be 20/81 as the others said.

Anonymous

Anonymous Tue 22 Jun 2021 23:57:08 No.13312118 Report

Quoted By: >>13312124

>>13312078
Messed that up haha, one more go
I suppose, they’re not independent. So I assume P(A) + P(B) will be in the equation for this Ptotal(B), but this is all determinate on the chance of P(A) happening. So, P(A) • (P(A) + P(B))?
Gives 44.4%. Overthinking or underthinking?

Anonymous

Anonymous Tue 22 Jun 2021 23:58:57 No.13312124 Report

Quoted By: >>13312129 >>13312148

>>13312104
>>13312113
>>13312118
IS 20/81 CORRECT OR NOT?

Anonymous

Anonymous Wed 23 Jun 2021 00:01:38 No.13312129 Report

Quoted By:

>>13312124
Yes, because your second problem statement is different and contains more information, the information being that P(plays B| loses A ) = 0. So 20/81 is correct. But that's a different problem than the OP.

Anonymous

Anonymous Wed 23 Jun 2021 00:02:04 No.13312132 Report

Quoted By:

50/50

Anonymous

Anonymous Wed 23 Jun 2021 00:05:56 No.13312148 Report

Quoted By:

>>13312124
It was my initial thought, assuming they were independent. But that’s not the case, I believe. In fact, the probabilities in the problem being similar is like no fluke but rather something to work with. Last guess; we ‘gained’ 1/9 or 11.1% fucking around with division and multiplication of P’s A and B also got me 11.1% percent.

Anonymous

Anonymous Wed 23 Jun 2021 00:12:33 No.13312175 Report

Quoted By:

>>13311837
Unknown since you only gave us probability conditioned on A. What if B can happen without A?

Anonymous

Anonymous Wed 23 Jun 2021 03:09:15 No.13312862 Report

Quoted By:

>>13312045
not relavant.

Anonymous

Anonymous Wed 23 Jun 2021 03:11:41 No.13312870 Report

Quoted By: >>13312891

>>13311837
under god all things are possible.

Anonymous

Anonymous Wed 23 Jun 2021 03:17:02 No.13312886 Report

Quoted By: >>13315039

>>13312078
>20/81 is not the correct answer. Read the thread.
Yes it is!

Anonymous

Anonymous Wed 23 Jun 2021 03:17:46 No.13312891 Report

Quoted By:

>>13312870
But not all things are probable

Anonymous

Anonymous Wed 23 Jun 2021 12:48:48 No.13314453 Report

Quoted By:

>>13311837
the probability of B happening is at least 20/81

Anonymous

Anonymous Wed 23 Jun 2021 15:12:42 No.13314810 Report

Quoted By:

>>13311837
Can't answer, not enough information. Defaulting to 50/50, it either happens or it doesn't

Anonymous

Anonymous Wed 23 Jun 2021 16:22:38 No.13315039 Report

Quoted By: >>13316779

>>13312886
Wrong. Again, read the thread.

Anonymous

Anonymous Wed 23 Jun 2021 17:24:01 No.13315230 Report

Quoted By:

What’s happening here is that we’re all assuming OP has the correct answer, that isn’t 20/81. Looking at some of the posts in the thread it seems OP is genuinely asking if it’s actually 20/81, rather than rhetorically asking.

Anonymous

Anonymous Wed 23 Jun 2021 18:28:59 No.13315428 Report

Quoted By:

>>13312047
This

Anonymous

Anonymous Wed 23 Jun 2021 18:49:10 No.13315528 Report

Quoted By: >>13315639 >>13319426

>>13311837
You use Bayes theorem.
$\mathbb{P}(B\vert A) = \frac{\mathbb{P}(A\vert B)\cdot \mathbb{P}(B)}{\mathbb{P}(A)}$
And you know
$\mathbb{P}(A)= 4/9$
$\mathbb{P}(B\vert A)= 5/9$
then
$5/9 = \frac{\mathbb{P}(A\vert B)\cdot \mathbb{P}(B)}{4/9}$
now isolate $\mathbb{P}[\math]<br />and you get<br /><script type="math/tex">\mathbb{P}(B) = \frac{20}{81\cdot \mathbb{P}(A\vert B)}$

Anonymous

Anonymous Wed 23 Jun 2021 19:13:39 No.13315626 Report

Quoted By:

>>13311837
20/81

Anonymous

Anonymous Wed 23 Jun 2021 19:15:18 No.13315632 Report

Quoted By:

>>13312013
>using percentage instead of using fractions
loser

Anonymous

Anonymous Wed 23 Jun 2021 19:17:26 No.13315639 Report

Quoted By:

>>13315528
/thread

Anonymous

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Anonymous Wed 23 Jun 2021 19:40:13 No.13315711 Report

Quoted By: >>13315995

>>13312089
This scenario cannot be described with probabilities. Probability is a concept for random experiments that can be repeated again and again infinitely. The event of teams playing against each other is singular. Speaking of probabilities in this context only shows you're a brainlet.

Anonymous

Anonymous Wed 23 Jun 2021 20:49:20 No.13315995 Report

Quoted By:

>>13315711
Haha I like you, you think exactly like me. It's so annoying seeing people talk about probabilities of events that only come up once, especially in animes "there's 95.8% chance she is going to kiss him" and other numbers pulled out of their ass.

Anonymous

Anonymous Thu 24 Jun 2021 01:03:18 No.13316779 Report

Quoted By: >>13318754

>>13315039
Read the thread, it's definitely 20/81.

Anonymous

Anonymous Thu 24 Jun 2021 14:51:03 No.13318754 Report

Quoted By: >>13319426

>>13316779
Read the thread. It's not 20/81

Anonymous

Anonymous Thu 24 Jun 2021 15:11:58 No.13318807 Report

Quoted By:

Anonymous

Anonymous Thu 24 Jun 2021 18:18:46 No.13319426 Report

Quoted By:

>>13318754
It's definitely 20/81. Why aren't you reading the thread?

>>13315528

El Arcón

El Arcón Thu 24 Jun 2021 18:19:47 No.13319430 Report

Quoted By:

What is the probability for B if A doesn't happen?

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