Two prophets

Flawed question.
They're prophets, they can't be wrong otherwise they wouldn't be prophets

Not enough information given. I need to know the prior probability of the end of the world.

Well ,i'm sorry.But that's not the correct answer.

You need to calculate the probability of a conditional probability, that is, the correct probability of the two prophets when the results of the two prophets are consistent.

First prophet is 9:1 evidence for.
Second prophet is 7:3 evidence against.
We've had nukes for 26260 days and haven't blown ourselves up yet, so let's estimate the prior odds of EoW as 1:26261 by Bayes-Laplace, which update to 21:26261 or 21/26282. This is bullshit, though, because in all likelihood prophet #1 picks questions anyone could guess the answer to and guesses based on his worldly knowledge rather than some independent oracle, prophet #2 probably deliberately picks prophecies where you would expect him to be wrong (e.g. one random date out of many possible dates), there are other EoW scenarios, and nukes aren't exactly EoW anyway.

You're fucking retarded then

100% or 1. Whichever you prefer. A world ending is inevitable, not because of a prophet or diety...but because of entropy.

60%

0.9+0.3i

p(worldend) * p(prophet1) * (prophet2)
0.5*0.9*0.3 = 0.135 or 13.5%

Protip: the statement given does not imply that P(fate of world=x | prophecy=x) = 0.9 (or 0.3), it only implies that P(prophecy=x | fate of the world = x) = 0.9 or 0.3.

Interesting.

100%, world ends no matter what these retards say as they specified no time frame.

Another mistake of mine: Nukes have been used twice, so the prior odds would be 3:26261, a bit higher. But it might make more sense to count since Russia got nukes.

79%
90%*30%+(1-90%)*(1-30%)=34%
All correct-27%
All wrong-7%
So 27%/34%=79%
That's the answer.

100%; the sun will destroy it given enough time.

There is a 100% chance that the world will eventually end.

I believe this to be the correct answer.

Let's say we have 100 marks and we must place the odds. Becouse first prophet is right in 9 of 10 cases and second 3 in 10 cases we share the marks 9:3 i.e 75 marks to first and 35 marks to second
From first person's advise, we put 67,5 marks to world's end and 7,5 marks to world will continue.

From second person's advise we put 10,5 marks world's end and 24,5 marks to world will continue.

So we have 78 marks for world's end.

>Nukes have been used twice

In war, yes. But just for fun, and not relevent really to your point, this video shows the sites of all known nuclear detonations... it's an interesting watch

youtube.com/watch?v=310-GYiitpM

But there are millions of people all over the globe who think the world is about to end, millions more that think it is not going to end until some distant epoch when the sun explodes or the universe contracts or whatever, in addition to the millions who don't give it much thought.

All of these people predict other things every day (I think it is going to rain, That chicken dinner looks like it will be good, I'ma get laid tonight...) and thus have some track record of how correct their other predictions have been.

The world, of course, does not give a shit about that -- it will end when it ends, regardless of whether 0 people prophesy about it correctly, or 100% of people call it to the second. or any mix in between. The accuracy of various people making other predictions on other topics has no impact on when the world will end.

>assuming they predict independently despite no implication
>not considering that the hallucinogens they take have similar effects on their brain which counts against independence
>"b-but your the brainlet"

Bayes rule. Next?

Caculate

Biblical prophecy is 100% accurate, precise and correct, and states exactly how the world will end.

So, 100%.

>What's the probability of the end of the world?
As a CS major.. I recognize the problem in your algorithm

this a halting problem...
The world may never end... you could wait 1000 years and say world will not end then it does next day
The end of the world is unpredictable

0%

world ends are bullshit

The smart money is always on 0%. If the world doesn't end, you win. If it does end, it's not like you'll be around to know that you were wrong.

This makes a lot of sense. The other guy being 30% means he is actually lowering the chance of it happening.

did he die?

Okay, so we actually have only two possibilities: either they are both wrong or both right.

If the world ends then they are both right, and the chance of that happening is 0.3 * 0.9 = 27%

If the world doesn't end then they are both wrong. The chance of that happening is 0.1 * 0.7 = 7%

So the chance of the world ending is 27 of (27+7), and that is 27/34 ~=~ 79.4%

>two prophets
>they all
They both, surely

!00%. The world will eventually end

>Biblical prophecy is 100% accurate

" I will make thee a terror, and thou shalt be no more: though thou be sought for, yet shalt thou never be found again, saith the Lord God."

-Ezekiel 26:21

How will Christfags ever recover?

79%

Accuracy only tells about their prophecys which could be checked by the time of the declaration of said accuracy. Has nothing to do with any probability of anything.
Just as the probability of a given number on any real dice isnt 1/6

Sorry, that wasnt expressed clearly. It COULD be 1/6, but no one will ever be able to be sure of that

OP here, the correct answer is 27% :)

100% The only actual question, which was not posted in the op, is WHEN. The prophets are irrelevant.

^^^^

pals, they have to both be right in order for this to work. the chances of them both being right are .9*.3

This makes sense once you realize that the shitty prophet is so shitty that it actually makes the first prophet less likely to be right if he agrees with him.

Dont we still need the actual probability of the world ending? Given that we are calculating conditional probability

Why should shitty profit Matter? WELL, Suppose shitty profit was always wrong ... then 90% profit wouldn't matter. TARDFAGS

Should we also factor in the guy listening to the prophet who admits he has no clue. So .9x.3x0=wtf

they'd burn those prophets for witchcraft here in Poland so I'd say 0%

which .9*.3

= .27

why did you say they were wrong then you faggot?

1:1

the sun will destroy earth when it expands in 11 bil years

Yes

if a 3rd one who guesses correctly 0% of the time is factored it still makes sense to multiply as long as they are independent

if they all guess it happens then its .9*.3*0, well if the 0% correctness guesses it happens, it wont happen with probability 1, so it happens with probability 0

0% cause they are lunatics high on acid claiming to be prophet

No.. you can see him drawing breath...
but DAMN.. Roo don't play
Do NOT fuck with a mature Roo, he will choke your ass out

no??

someone who isn't making a prediction has zero bearing on this. that being said, if a random dude just fucking guessed and said yes like the other two prophets, the equation would be (.9*.3)^2. This is because the odds of the prophets being correct--and, thus, the odds of the guy being correct if he agrees with them--haven't really changed.

it's the union of the two probabilities;
0.9 + 0.3 - (0.3*0.9) = 0.93

...

depends how you define accuracy. In a strictly mathematical sense having the shitty prophet agree with you means there's a 70% chance the opposite will happen, thus the shitty prophet grants 70% chance the world will be fine, and the accurate prophet says 90% the world will go under.
The somewhat counterintuitive result is that having the shitty prophet agreeing with you gives you less chance of being right.

Following this but sharing the coins 9:7, I get 63.75%

It's 93% if you include calculation for either one to be correct. But, you can't have a result of one being correct and the other wrong, because they both predicted the same thing.

The world will eventually end, so 100%

But becouse we know she is more than 50% wrong, one can actually prophet the opposite with 70% accuracy. So one prophet actually says world will not end and this prophecy has 70% chance to be right. The other says that the world will end with 90% accuracy. So we can conclude that the world will end with few procent units more that 50%. Say 60-80%

>my unfounded belief validates your mathematics

P{both correct} = 0.9*0.3 = 0.27 = p
P{both incorrect} = 0.1*0.7 = 0.07 = q
P{world ends} = p/(p+q) = 0.27/ 0.34 = 0.79

Once upon a time, a wise prophet who had a 99% chance of prediction predicted the end of the world. After everyone ridiculed him, he summoned 999 dead prophets, who also had a 99% chance of prediction, to defend his case. But to their dismay, they were embarrassed when the world had not ended. Everyone laughed as the prophets muttered,"but...99%" to which the mathematicians responded," HA! But you only had a 0.0043% of predicting correctly!

>What's the probability of the end of the world?

100%, as the world will end someday. Thats a sure bet, so everyone pretending to be a mystic or psychic can cash in on that once every few generations.

Suppose the first prophet had 100% accuracy and the second prophecy had 1% accuracy. If you simply multiply 1% and 100% you get 1%, yet this can't be true because the first prophet is 100% right. And if the first prophet was 99% certain and the second prophet was 0% accurate, it would mean the chance of the end of the world is 0%. The second case could be a multiplication but the first case could not. So there must another relation, thus consider this: Prophet A is 50% and Prophet B is 49%. This means there is a chance of 51% Prophet B is wrong. So if A is 90% and B is 30%, B is 70% against the world's end and A is 10% against the world's end. Thus we can't take the highest value and leave the rest out of it, can we? 90% the world ends versus 70% the world doesn't end is wrong.. Real accuracy increases over or under 50%. So you are left with this question: Is A 90% and B 30% even possible? You know there are impossible situations i.e. the first prophet is 100% and the second prophet is 0%. But this is different and a very realistic scenario. Considering B knows his odds, that B is actually betting on the world not ending with 70% accuracy, accuracy can be seen as statistical proportion after the possible event, that is, after the world either ending or not, A will be right 9:1 of times while B will be right 7:3 of times. A solution is that the times count is different, that one makes more predictions than the other, which of course means that one is older than the other(see picture). If A is older, he is twice events older, and if B is older, he is 2.4x events older. With these age differences you can weigh an average: for the minimum age 10, chance = 2.4 * 70 + 2.0 * 90 / 4.4 = 79 + 9/99 = 79.0909090... %

It's 60 percent you fucking gumrakers.

ouch

When y > x

p = x/(1-y+x)

p = 0.3/0.4 = 0.75

The question is flawed and unanswerable.

Either they are both right or wrong and do not
affect eachothers singular probablity of being right.

90% doesn't equal 30%.

You'd probably want to use dempster-schafer for this

dempster-schafer?

Nope.

1 on a long enough timescale for a suitable definition of "the world"

100%
The world is going to end eventually.

>what is causation

27%

P(end of the world):

0.9*0.3=0.27=27%

Only correct answers ITT. Really Veeky Forums?

Wrong, it's
1-(1-0,9)*(1-0,3)=1-0,07=0,93
->93%

Many of you seem to believe that if one prophet who is 90% correct says something, there is a 90% chance he is correct, as long as another prophet does not say the same thing. If a 30% accurate prophet comes along and agrees, suddenly the odds go down!

This makes no sense.

Your mathematics are being misapplied.

What happens if you have two prophets, one who is 100% correct and one who is 0% correct, both saying the world will end?