A sick math problem I can't seem to wrap my brain around.

[Dogma]

Took me over 600 hours camping Jail in KC before I got my first Tstaff drop. That's only counting actual hours camping it tho. I haven't tried keeping track since.

Got a few leveling on random toons in the zone and a few logging in drunk at 2am just wandering around.

Then again I was randomly given a Spirit Wracked Urn for free also. So idk. Luck is weird.

Be good, hope for the best and be okay when it isn't. Bout all you can do.

[Ruien]

The OP seems to be asking how to calculate the number of attempts at a mob before getting at least N drops, given a drop rate.
That is the cumulative distribution function (CDF) of a negative binomial distribution. Scilab has this as the cdfnbn function.

This gives us the number of failures before a certain number of successes. The total number of attempts is the sum of the failures and successes.

For example, if we want 3 drops at 8% success per attempt, then it will require 48 attempts to be 75% sure of getting them:

successes = 3
success_chance = 0.08
confidence = 0.75
attempts = successes + cdfnbn("S", successes, success_chance, 1.0-success_chance, confidence, 1.0-confidence)

    attempts  =   48.031623

If the average time between attempts (including fighting) is 90 minutes, then this will require 72 hours. To be 95% sure, it increases to 77 attempts (115.5 hours).

If we want 3 drops at 1% success per attempt, then it will require 391 attempts to be 75% sure of getting them:

successes = 3
success_chance = 0.01
confidence = 0.75
attempts = successes + cdfnbn("S", successes, success_chance, 1.0-success_chance, confidence, 1.0-confidence)

    attempts  =   391.07841

If the average time between attempts (including fighting) is 6 minutes, then this will require 39.1 hours. To be 95% sure, it increases to 628 attempts (62.8 hours).

A few results:

1% chance, 1 success, 50% confidence: 69 attempts
1% chance, 1 success, 75% confidence: 138 attempts
1% chance, 1 success, 95% confidence: 298 attempts
1% chance, 1 success, 99% confidence: 458 attempts

5% chance, 1 success, 50% confidence: 14 attempts
5% chance, 1 success, 75% confidence: 27 attempts
5% chance, 1 success, 95% confidence: 58 attempts
5% chance, 1 success, 99% confidence: 90 attempts

10% chance, 1 success, 50% confidence: 7 attempts
10% chance, 1 success, 75% confidence: 13 attempts
10% chance, 1 success, 95% confidence: 28 attempts
10% chance, 1 success, 99% confidence: 44 attempts

This is sort of off the top of my head; it might be wrong. Can anyone confirm?

[magnetaress]

Originally Posted by Dogma [You must be logged in to view images. Log in or Register.]

Took me over 600 hours camping Jail in KC before I got my first Tstaff drop. That's only counting actual hours camping it tho. I haven't tried keeping track since.

Got a few leveling on random toons in the zone and a few logging in drunk at 2am just wandering around.

Then again I was randomly given a Spirit Wracked Urn for free also. So idk. Luck is weird.

Be good, hope for the best and be okay when it isn't. Bout all you can do.

Originally Posted by Ruien [You must be logged in to view images. Log in or Register.]

The OP seems to be asking how to calculate the number of attempts at a mob before getting at least N drops, given a drop rate.
That is the cumulative distribution function (CDF) of a negative binomial distribution. Scilab has this as the cdfnbn function.

This gives us the number of failures before a certain number of successes. The total number of attempts is the sum of the failures and successes.

For example, if we want 3 drops at 8% success per attempt, then it will require 48 attempts to be 75% sure of getting them:

successes = 3
success_chance = 0.08
confidence = 0.75
attempts = successes + cdfnbn("S", successes, success_chance, 1.0-success_chance, confidence, 1.0-confidence)

    attempts  =   48.031623

If the average time between attempts (including fighting) is 90 minutes, then this will require 72 hours. To be 95% sure, it increases to 77 attempts (115.5 hours).

If we want 3 drops at 1% success per attempt, then it will require 391 attempts to be 75% sure of getting them:

successes = 3
success_chance = 0.01
confidence = 0.75
attempts = successes + cdfnbn("S", successes, success_chance, 1.0-success_chance, confidence, 1.0-confidence)

    attempts  =   391.07841

If the average time between attempts (including fighting) is 6 minutes, then this will require 39.1 hours. To be 95% sure, it increases to 628 attempts (62.8 hours).

A few results:

1% chance, 1 success, 50% confidence: 69 attempts
1% chance, 1 success, 75% confidence: 138 attempts
1% chance, 1 success, 95% confidence: 298 attempts
1% chance, 1 success, 99% confidence: 458 attempts

5% chance, 1 success, 50% confidence: 14 attempts
5% chance, 1 success, 75% confidence: 27 attempts
5% chance, 1 success, 95% confidence: 58 attempts
5% chance, 1 success, 99% confidence: 90 attempts

10% chance, 1 success, 50% confidence: 7 attempts
10% chance, 1 success, 75% confidence: 13 attempts
10% chance, 1 success, 95% confidence: 28 attempts
10% chance, 1 success, 99% confidence: 44 attempts

This is sort of off the top of my head; it might be wrong. Can anyone confirm?

These posts are so awesome and I have total and absolute faith in them.

And ya, nothing is certain. So it's possible to never ever get an AC ring. (scary)

Thank you so much for the lengthy math explanation. That is what I was most curious about. I have a very hard time understanding that stuff, and my math teach gave me a passing grade by 1 point because she just didn't want to ever see me again. So I greatly appreciate you taking the time to try and teach me.

[Topgunben]

Originally Posted by magnetaress [You must be logged in to view images. Log in or Register.]

An 8% chance every 90 minutes.

vs

An 1% chance every 6 minutes.

8/90 = 0.0888888888888889% chance per minute?

and

1/6 = 0.1666666666666667% chance per minute?

How insane on a scale of 1-10 is this math? [You must be logged in to view images. Log in or Register.] [You must be logged in to view images. Log in or Register.]

Here's the crazy thing my man:

8% chance over 90 minutes not so good.

So lets say you really want that item that has that % of chance to drop over that amount of time.

Well, even after 15 hours of camping said item, you still have a 43.4% chance that the item will not have dropped. (.92^10) = .434 & ((10 x 90)/60) = 15

After 30 hours, there is still a 18.8% chance the item will not have dropped.

After 60 hours of poopsocking, there is still a 3.56% chance the item will not drop.

It's this type of analysis that keeps most sane people from trying too hard to compete at the upper levels.

[magnetaress]

Originally Posted by Topgunben [You must be logged in to view images. Log in or Register.]

Here's the crazy thing my man:

8% chance over 90 minutes not so good.

So lets say you really want that item that has that % of chance to drop over that amount of time.

Well, even after 15 hours of camping said item, you still have a 43.4% chance that the item will not have dropped. (.92^10) = .434 & ((10 x 90)/60) = 15

After 30 hours, there is still a 18.8% chance the item will not have dropped.

After 60 hours of poopsocking, there is still a 3.56% chance the item will not drop.

It's this type of analysis that keeps most sane people from trying too hard to compete at the upper levels.

Ya.

The EQ gods smiled at me when I logged in, I was running my wiz to lake rathe to get her bone rod from the skele dudes for her clicky debuff staff...

Low and behold AC was up and roaming, LUCK.

I try not to camp these things, I camped it on my necro cuz I definately wanted to do this for msyelf, and i didnt mind if it took days. Glad I wasn't pvpd out of oot otherwise I may have QQ'd or played an alt.

Again, Luck, who knows. I feel good, and I feel more resilient toward these camps now. I guess my best advice is dont get your heart set... on something in a specific time frame, give it space to come when it comes. Or allow urself to farm the plat for an MQ. Thats what its there for!