Thread: Probability

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  1. #1
    Dreadlord Niku's Avatar
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    Probability

    So I am currently farming for the Drake of the North Wind in Vortex Pinnacle and I have cleared the place 77 times since I started counting.
    The drop chance is 0.78% according to wowhead and I'll trust that it's either that or close to it. I'm using this article http://wow.joystiq.com/2010/01/13/dr...ity/#continued to calculate the probability for the mount to have dropped during the course of my 77 runs (at the moment: 45.28075 percent). But seeing as I am not even remotely talented when it comes to mathematics, my mind is having an issue wrapping itself around the whole ordeal.

    Everytime I kill the dragon the drop rate is it's fixed 0.78%, that does not rise or fall on any new kill. On the other hand, the number of times I have killed him rises and I should have had an overall increase chance for it to have dropped... so should I get more excited about the next run and the run after that? The drop rate is unchanged, but it feels as if I have a higher chance to get it everytime... but I don't.
    When I am at 500 runs and let's assume for arguments sake I have not had it drop yet, the chance that I would have seen it within the number of my runs is now at 98%. In such a scenario, should I expect it to drop any run now? Or is that foolish since the probability is still 0.78% which doesn't seem promising at all.

    Ultimately I don't know what to ask. I believe it boils down to "Should I get more excited since it's more likely to drop?".
    "The world is filled with lies! Thou shalt not kill. Thou shalt not steal. Thou shalt not bear false witness. Thou shalt not commit adultary. These are all lies, deceptions. I don't want to be killed. I don't want to be victim of theft. That is why they use lies like justice and moral to protect their weak selves. The original truth is the survival of the fittest. One must devour it all, wether it be other humans, wealth, power or the world itself! All hail Britannia!" - Charles vi Britannia

  2. #2
    The chance of it dropping doesn't increase no matter how many times you do it, it's still a 0.78% chance each time. That said, if you keep going you should eventually get it, but if you stop you'll never get it, so keep going and hope for good luck!

  3. #3
    Fluffy Kitten Annoying's Avatar
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    By probability you could theoretically kill it until the servers shut down without ever seeing it.
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  4. #4
    Dreadlord Niku's Avatar
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    Quote Originally Posted by Annoying View Post
    By probability you could theoretically kill it until the servers shut down without ever seeing it.
    I get that, but the chance of that happening would be immensly tiny.
    "The world is filled with lies! Thou shalt not kill. Thou shalt not steal. Thou shalt not bear false witness. Thou shalt not commit adultary. These are all lies, deceptions. I don't want to be killed. I don't want to be victim of theft. That is why they use lies like justice and moral to protect their weak selves. The original truth is the survival of the fittest. One must devour it all, wether it be other humans, wealth, power or the world itself! All hail Britannia!" - Charles vi Britannia

  5. #5
    You need to think backwards. It is still 0.78% for the drop each time you do it. HOWEVER, your chance of it "not dropping" 77x in a row is what you are really calculating. So you are adding a dimension to the calculation.

    The technical answer is "Yes, you should get more exited each time. The reason is that the chance of it NOT dropping again is less than the previous time."

  6. #6
    flip 2 coins,

    50% fixed chance to get ether heads or tails,in this case heads = loot
    BUT, whats the chance to get two tails in a row (thus no loot drop)? thats the chance you get from the probabilty calculator but with different numbers

  7. #7
    The only thing you can say is that if you were to run 77 more runs, you can expect to have a 44% to receive the mount at some point during those 77 runs. Each individual run only has .78% chance and not getting it will not increase your chances.
    Quote Originally Posted by yjmark View Post
    You need to think backwards. It is still 0.78% for the drop each time you do it. HOWEVER, your chance of it "not dropping" 77x in a row is what you are really calculating. So you are adding a dimension to the calculation.

    The technical answer is "Yes, you should get more exited each time. The reason is that the chance of it NOT dropping again is less than the previous time."
    This is absolutely incorrect.

    For example, assume a flip a coin 9 times and they are all tails. My chances of getting 10 tails in a row is minuscule (1/1024 or 0.09765625%). Does that mean my chances at a heads next flip is almost 100%? Nope, it's 50%.

    An easy way to think about it, is events in the past cannot change. They have a 100% chance of having happened. The past will not affect your future probability.
    Last edited by Imperviable; 2013-11-18 at 11:26 PM.

  8. #8
    The actual probability of it dropping is most likely 1%.

  9. #9
    Quote Originally Posted by Niku View Post
    Or is that foolish since the probability is still 0.78% which doesn't seem promising at all.
    This is the proper answer. You're simply 'rolling the dice' each time you kill it and the current roll has exactly zero effect on the previous, or next, roll.

  10. #10
    When I am at 500 runs and let's assume for arguments sake I have not had it drop yet, the chance that I would have seen it within the number of my runs is now at 98%. In such a scenario, should I expect it to drop any run now? Or is that foolish since the probability is still 0.78% which doesn't seem promising at all.


    That 98% simply means that "Over 500 runs, the chance of it NOT dropping is 2%"

    The problem is that once you've done those 500 runs and not had the mount drop, they're gone. Over. In the past. You don't get to combine your next run into the last 500 runs and then calculate the probability based on a 501 run set. Your 501st run still has that 99% chance of it not happening.



  11. #11
    It's .78% every time, fixed probability is well...fixed.

  12. #12
    Ultimately I don't know what to ask. I believe it boils down to "Should I get more excited since it's more likely to drop?".
    No, but the article you're looking at is accurate.

    Try thinking of it another way: if 100 people start farming the mount, one lucky bastard will get it in his first run. By 77 runs, 45 of them will have it. And after 450 runs, one poor sod will still not have it. (This assumes the numbers adhere perfectly with the statistics, which in a group of 100 they probably won't. But it will be close.)

    What the calculator in the article does is work out the chance of having seen a drop in the number of runs so far. It's important to note this never reaches 100%.

    Personally I reached 125 runs before giving up and getting the Silver Covenant Hippogryph. Statistically speaking I probably would have seen the mount drop in the time it took me to farm the seals, but I'd had enough of relying on RNG. At least the hippogryph is guaranteed.
    Last edited by 7seti; 2013-11-18 at 11:51 PM.

  13. #13
    given a 1% chance for the item to drop:
    after 30 runs your chance of NOT having it is: 0.99^30 = 0.74 (~26% chance to actually have it by then).
    after 100 runs your chance of NOT having it is: 0.99^100 = 0.37 (~63% chance to actually have it by then).

    however these values do not desribe your chance to drop the item in run "X" but rather desribe the relative amount of a _large_ group of people, that will have it by then.
    the thing about statistics is: it only works for large groups.

  14. #14
    It's still only 1% that it will drop ON THAT RUN, but your chance of getting it in X runs increases as X increases. So... yeah. Probability is confusing. Suffice it to say, you keep doing it and eventually it happens.

    If it helps, I got mine by accident during Cata and won the roll. My pants were full of jizz for the rest of the expansion. No luck with the Stonecore one though
    Quote Originally Posted by Tojara View Post
    Look Batman really isn't an accurate source by any means
    Quote Originally Posted by Hooked View Post
    It is a fact, not just something I made up.

  15. #15
    Dreadlord Niku's Avatar
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    Quote Originally Posted by Mormolyce View Post
    It's still only 1% that it will drop ON THAT RUN, but your chance of getting it in X runs increases as X increases. So... yeah. Probability is confusing. Suffice it to say, you keep doing it and eventually it happens.

    If it helps, I got mine by accident during Cata and won the roll. My pants were full of jizz for the rest of the expansion. No luck with the Stonecore one though
    I got the Vitreous Drake on my 28th run.
    "The world is filled with lies! Thou shalt not kill. Thou shalt not steal. Thou shalt not bear false witness. Thou shalt not commit adultary. These are all lies, deceptions. I don't want to be killed. I don't want to be victim of theft. That is why they use lies like justice and moral to protect their weak selves. The original truth is the survival of the fittest. One must devour it all, wether it be other humans, wealth, power or the world itself! All hail Britannia!" - Charles vi Britannia

  16. #16
    Bloodsail Admiral Daedelus's Avatar
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    Probability for dummies:

    Flip a coin - chance to get heads is 0.5
    Flip a coin 1000 times - chance to get heads on the 1000th flip is still 0.5

    Do a dungeon - chance to get a mount is 0.0078
    Do a dungeon 1000 times - chance to get the mount on the 1000th run is still 0.0078


    Hope that helps. Probability is not hard

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    Quote Originally Posted by Mormolyce View Post
    It's still only 1% that it will drop ON THAT RUN, but your chance of getting it in X runs increases as X increases. So... yeah. Probability is confusing. Suffice it to say, you keep doing it and eventually it happens.
    Wrong, wrong, wrong.

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    Quote Originally Posted by megabeat View Post
    flip 2 coins,

    50% fixed chance to get ether heads or tails,in this case heads = loot
    BUT, whats the chance to get two tails in a row (thus no loot drop)? thats the chance you get from the probabilty calculator but with different numbers
    Again, wrong. The previous coin flip has no bearing on subsequent flips. You're confusing the probability of getting a head on a coin flip (0.5) with the probability of getting two tails in a row (0.5^2) = 0.25. The two events are unrelated.

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    Quote Originally Posted by Niku View Post
    I get that, but the chance of that happening would be immensly tiny.
    No it wouldn't. You could run it 1,000,000 times and every time your chance is 0.0078

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    Quote Originally Posted by yjmark View Post
    You need to think backwards. It is still 0.78% for the drop each time you do it. HOWEVER, your chance of it "not dropping" 77x in a row is what you are really calculating. So you are adding a dimension to the calculation.

    The technical answer is "Yes, you should get more exited each time. The reason is that the chance of it NOT dropping again is less than the previous time."

    Again, wrong. That's not the probability you're interested in. What you want to know is "What is the chance of it dropping?", which is 0.0078 every time.


    I don't understand why this seems to be so hard for some people to grasp.
    Last edited by Daedelus; 2013-11-19 at 01:20 AM.

  17. #17
    Quote Originally Posted by Niku View Post
    So I am currently farming for the Drake of the North Wind in Vortex Pinnacle and I have cleared the place 77 times since I started counting.
    The drop chance is 0.78% according to wowhead and I'll trust that it's either that or close to it. I'm using this article http://wow.joystiq.com/2010/01/13/dr...ity/#continued to calculate the probability for the mount to have dropped during the course of my 77 runs (at the moment: 45.28075 percent). But seeing as I am not even remotely talented when it comes to mathematics, my mind is having an issue wrapping itself around the whole ordeal.

    Everytime I kill the dragon the drop rate is it's fixed 0.78%, that does not rise or fall on any new kill. On the other hand, the number of times I have killed him rises and I should have had an overall increase chance for it to have dropped... so should I get more excited about the next run and the run after that? The drop rate is unchanged, but it feels as if I have a higher chance to get it everytime... but I don't.
    When I am at 500 runs and let's assume for arguments sake I have not had it drop yet, the chance that I would have seen it within the number of my runs is now at 98%. In such a scenario, should I expect it to drop any run now? Or is that foolish since the probability is still 0.78% which doesn't seem promising at all.

    Ultimately I don't know what to ask. I believe it boils down to "Should I get more excited since it's more likely to drop?".
    I stopped at 200 kills during the Theramore event time. Couple weeks later I got my red storm drake. Never again.

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    Quote Originally Posted by Daedelus View Post
    Probability for dummies:

    Flip a coin - chance to get heads is 0.5
    Flip a coin 1000 times - chance to get heads on the 1000th flip is still 0.5

    Do a dungeon - chance to get a mount is 0.0078
    Do a dungeon 1000 times - chance to get the mount on the 1000th run is still 0.0078


    Hope that helps. Probability is not hard

    - - - Updated - - -



    Wrong, wrong, wrong.

    - - - Updated - - -



    Again, wrong. The previous coin flip has no bearing on subsequent flips. You're confusing the probability of getting a head on a coin flip (0.5) with the probability of getting two tails in a row (0.5^2) = 0.25. The two events are unrelated.

    - - - Updated - - -



    No it wouldn't. You could run it 1,000,000 times and every time your chance is 0.0078

    - - - Updated - - -




    Again, wrong. That's not the probability you're interested in. What you want to know is "What is the chance of it dropping?", which is 0.0078 every time.


    I don't understand why this seems to be so hard for some people to grasp.
    The chance that is has not dropped by the 78th time is lower than the chance it had not dropped by the 77th. The chance it has has not dropped on the first run for a player farming it is high. The chance it has not dropped by the 1000th run is very low. The chance it drops on the individual run is the same. And if you dont think about it like the chance of you reaching X number of kills and not having it being super low then you will probably start to hate life around the 40th kill

  18. #18
    Scarab Lord nightfalls's Avatar
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    Your chance of getting it your next run is the same as the chance of getting it your first run. That said, it's about a 1% drop rate. If you run the place 458 more times, you will (with a 99% chance) get the mount.

    Also: There is no such thing as "chance it had or hadn't dropped." Once you run, "chance" is over and the only thing you know is whether it did or didn't drop. You only talk of chance if it drops at least once the next 100 or 1,000 runs.

  19. #19
    The probability of getting it on your first run is about the same as the probability of not getting it on 450-500 runs. Interesting, eh?

  20. #20
    Scarab Lord nightfalls's Avatar
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    Quote Originally Posted by Dilbon View Post
    The probability of getting it on your first run is about the same as the probability of not getting it on 450-500 runs. Interesting, eh?
    458 runs to be precise.

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