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playing solo russian roulette -- question that affects a friends life playing solo russian roulette -- question that affects a friends life

07-26-2008 , 10:25 PM
I'm abstracting the details of this question from actual life events.... but this is the basic gist of what I want to compute.

A friend of mine is playing a solo version of russian roulette, but with a twist.

The capacity of the revolver is 13 rounds.

Every position in the revolver holds a bullet.

The bullets are of poor quality and will only fire with a probability of 2%.

What is the probability that my friend will die if he attempts to pull the trigger 13 times.
playing solo russian roulette -- question that affects a friends life Quote
07-26-2008 , 10:33 PM
Actually, I just saw the 'odds of 1 in a million' compounded thread.. which seems to be the same thing.. so is this right?

1 - (1 - 0.02) ^ 13 = 23%?
playing solo russian roulette -- question that affects a friends life Quote
07-26-2008 , 11:13 PM
yep that's it
playing solo russian roulette -- question that affects a friends life Quote
07-27-2008 , 10:19 AM
LOL,

no

A lot closer to 2%

Seriously people, 2% chance to fire everytime out of 13 how can you think its 23% ?
playing solo russian roulette -- question that affects a friends life Quote
07-27-2008 , 11:07 AM
Quote:
Originally Posted by Seb86
LOL, no. A lot closer to 2%. Seriously people, 2% chance to fire everytime out of 13 how can you think its 23% ?
I think you misunderstood the question. The friend dies if any of the bullets are good, not every bullet. The chance of every bullet is 1 in 1 followed by 22 zeros, about the same a dealing four royal or king-high straight flushes in a row from well shuffled five card decks.

A simple guess would be that 2% chance of dying each time, times 13 chances, gives 26% chance of dying. It can't be 2%.

0.36 is the expected number of good bullets. That is, if you did this 100 times, firing at a target so on one gets killed, there would be close to 26 bullets that fire. But that doesn't meant that 26% of guns fire at least one bullet.

76.9% fire no bullets, 20.4% fire one, 2.5% fire two and 0.2% fire three. So the chance of dying is 20.4% + 2.5% + 0.2% = 23.1% = 1 - 76.9%. But the expected number of good bullets is 20.4%*1 + 2.5%*2 + 0.2%*3 = 26%.
playing solo russian roulette -- question that affects a friends life Quote
07-27-2008 , 03:01 PM
Quote:
Originally Posted by bobdibble
I'm abstracting the details of this question from actual life events.... but this is the basic gist of what I want to compute.

A friend of mine is playing a solo version of russian roulette, but with a twist.

The capacity of the revolver is 13 rounds.

Every position in the revolver holds a bullet.

The bullets are of poor quality and will only fire with a probability of 2%.

What is the probability that my friend will die if he attempts to pull the trigger 13 times.
Please tell your friend NOT to do this if you are serious...terrible idea. The ~23.1% chance is correct, assuming that whether one bullet fires is independent of another firing and assuming that the 2% number is accurate.
playing solo russian roulette -- question that affects a friends life Quote
07-27-2008 , 04:45 PM
I doubt the real details actually involve a revolver because it's kinda hard to figure that the chance of it firing is EXACTLY 2%. Could easily be 5%, in which case, he may be in trouble.
playing solo russian roulette -- question that affects a friends life Quote
07-27-2008 , 09:17 PM
Well If I read this correctly there is 1 chance out of 13 each time to fire a bullet and IF that happens then only 2% chance that the bullet actually fires.

So probability of this to happen is 1/13 * .02 = .0015.

Probability of a bullet never firing in 13 shots is .0015^13
playing solo russian roulette -- question that affects a friends life Quote
07-28-2008 , 07:50 AM
Quote:
Originally Posted by Seb86
Well If I read this correctly there is 1 chance out of 13 each time to fire a bullet and IF that happens then only 2% chance that the bullet actually fires.

So probability of this to happen is 1/13 * .02 = .0015.

Probability of a bullet never firing in 13 shots is .0015^13
Nope, OP said that all chambers are full, and his friend is firing 13 times. Not just one chamber is full.
playing solo russian roulette -- question that affects a friends life Quote
07-29-2008 , 03:09 AM
Quote:
Originally Posted by Ninjah Poker
Nope, OP said that all chambers are full, and his friend is firing 13 times. Not just one chamber is full.
This is Polish roulette, not Russian.
playing solo russian roulette -- question that affects a friends life Quote
07-31-2008 , 12:09 AM
wtf 13 round revolver? wouldnt this be a semi automatic handgun then... which would change a lot of assumptions.
playing solo russian roulette -- question that affects a friends life Quote
07-31-2008 , 04:48 PM
Hey guys, was bored at work so I took the time to make a Monte Carlo experiment on MATLAB.

Check these results out...

Here is the code...

Quote:

%Attempting to kill yourself
%like Christopher Walken in Deer Hunter
%...but with a twist
%bkar824

clear
clf reset
hold on

p=.02; %Probability that a bullet will fire
chamberSize=13;
N=10000;

deadcount=0;

for ii=1:N

dead=0;
shotz(ii)=0;
while (dead==0 && shotz(ii)<chamberSize)
shot=rand;
if shot<p
dead=1;
deadcount=deadcount+1;
end
shotz(ii)=shotz(ii)+1;
end
deadcountavg(ii)=deadcount/ii;
end

plot(deadcountavg)
ProbabilityOfDeath=deadcount/N
plot(1:1:N,ProbabilityOfDeath)
Here is the resulting graph with the Monte Carlo experiment Death Percentage:

playing solo russian roulette -- question that affects a friends life Quote
08-01-2008 , 06:01 PM
I would've said less than the probability that we got all the way to post 12 before someone referenced Deer Hunter.
playing solo russian roulette -- question that affects a friends life Quote
08-03-2008 , 12:39 AM
lmfao @ variance good, and variance bad. AWESOME chart. and the "polish roulette" comment was great as well.
playing solo russian roulette -- question that affects a friends life Quote

      
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