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How Math Works


Mythbusting's Avatar


Mythbusting
05.14.2012 , 10:23 AM | #21
Quote: Originally Posted by Cerion View Post
Let me reiterate, as I do in every post like this, that I'm actually not a fan of the RNG system. It is precisely BECAUSE it is working as intended that I don't like it. You get a population, through no fault of their own, who gets screwed due solely to the laws of probability.
So very much agreed.

That current system also makes it ridiculously hard to distinguish between bugs and features (because it takes a fairly large sample size to distinguish chance variation from a true effect). I imagine customer service gets a fair number of reports from unlucky players, and so has a hard time tracking trends that are true bugs. So they send back canned responses, which is more like salt in a wound than a helpful reply. Badness all around.

rjkishida's Avatar


rjkishida
05.14.2012 , 10:27 AM | #22
Quote: Originally Posted by Paranitis View Post
I've noticed people complaining about the 20% or 10% Reverse Engineer chance, and then complaining they don't get something to happen within 5 or 10 tries.

Here's how math works, so you cannot complain:

You have an object that you want to RE. It has a 20% chance to cause you to learn a new schematic. You fail.
You have an object that you want to RE. It has a 20% chance to cause you to learn a new schematic. You fail.

If you take a 20 sided die, you have a 5% chance to roll any specific number. Just because you roll the wrong number, it doesn't mean that that wrong number is no longer available. It still means you have a 5% chance on your next roll to roll any specific number.

People are complaining and acting as if 20% chance means that if you fail 4 times, that the 5th time will work.

20% chance is not cumulative. It does not stack. It doesn't go 20% to 40% to 60% and so on.

That's why RNG is RNG.

If an item has a 1% chance to drop from a boss fight, and you've killed it 1 million times and it hasn't dropped yet, that doesn't mean it doesn't have a 1% chance to drop. It just means that every time you've fought it, you rolled one of the other 99% of numbers.
OK Mr Math genius. Calculate the odds of failing 30 times to get a schematic that you have a 20% chance to get. Then multiply that by the 30+ people who have posted threads about them doing 30+ tries without getting succeeding. What would the odds be of the 30 people having that failure rate?

Try and get out of that one.

Cerion's Avatar


Cerion
05.14.2012 , 10:40 AM | #23
Quote: Originally Posted by rjkishida View Post
OK Mr Math genius. Calculate the odds of failing 30 times to get a schematic that you have a 20% chance to get. Then multiply that by the 30+ people who have posted threads about them doing 30+ tries without getting succeeding. What would the odds be of the 30 people having that failure rate?

Try and get out of that one.
I've actually already calculated this here and in another thread. Roughly speaking, you'd expect in a population of 100,000 crafters, around 500 of them to have bad luck streaks of the order you're speaking of. In fact, the odds of 30 people having that failure rate is nearly certain.
Good will always triumph because Evil is lazy.

Cerion's Avatar


Cerion
05.14.2012 , 10:55 AM | #24
Quote: Originally Posted by Mythbusting View Post
So very much agreed.

That current system also makes it ridiculously hard to distinguish between bugs and features (because it takes a fairly large sample size to distinguish chance variation from a true effect). I imagine customer service gets a fair number of reports from unlucky players, and so has a hard time tracking trends that are true bugs. So they send back canned responses, which is more like salt in a wound than a helpful reply. Badness all around.
As a side note...think about the population of people on the Earth...7 billion. Now think about the everday events that happen by chance in our lives every day. Ever wonder why some people seem to 'have all the luck' while others claim to 'have the worst luck'. This 'luck' can be plotted as a normal distribution curve, a bell curve. Most people have average luck, but others have one, two, or three standard deviations from the norm. In a world with 7 billion people, you're simply going to have a certain small percentage of people who are really damn lucky. You can't tell who they will be ahead of time, only that they will exist.

anyway, that's food for thought.
Good will always triumph because Evil is lazy.

siegeshot's Avatar


siegeshot
05.14.2012 , 02:22 PM | #25
Quote: Originally Posted by Cerion View Post
Except that he entered the wrong parameters into the calculator. See my follow-up post.
Oh I know I totally agree. I read your follow-up also. Totally agree with you.

On a side note, as you know, you look at large populations and you start to see some interesting stuff on the outliers of the bell curve.
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venomlash's Avatar


venomlash
05.14.2012 , 03:20 PM | #26
OP, please read up on cumulative probability. Sure, having failed 30 times doesn't make the next attempt more likely to succeed. But failing many times in succession is very very unlikely.
Quote: Originally Posted by MichelleArcher View Post
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QuickBunnie's Avatar


QuickBunnie
05.14.2012 , 03:52 PM | #27
Actually, everyone should read up on cumulative probability - a lot of bad math in here.

Cerion has the math right.

Odds are multiplicative when calculating multiple events. This is the general formula for independent events:
Chance to get schematic = 1-((1-p)^n)
p = RE rate
n = number of items RE'd
When working with the formula, remember that the numbers are not % numbers. So 20% RE rate is 0.2, and a final probability of .64 is 64%

So if you have a 20% success rate, the probability getting a schematic by RE one item is 20%
Probability of getting one by RE 2 items is 36% (NOT 40%)
3 item is 48.8%
4 item is 59.04%
....
20 item is 98.85% chance
Please understand that. Out of ALL crafters that RE 20 items of a 20% item, 1.15% of them will NOT get a successful recipe.

So yes, you are very unlucky if you are RE 20+ items and not grabbing a recipe, but you are in the realm of possibility.

Let's put this another way.
If you want a 99.95% chance to RE a recipe, you need to RE:
34 items of a 20% chance
74 items of a 10% chance
150 items of a 5% chance

Even at 99.95%, 1 in every 2000 people will still not have a recipe.

beowulfe's Avatar


beowulfe
05.14.2012 , 04:23 PM | #28
There's two problem's here. 20% is immaterial when I go 60 items without a single RE success. This leads to the second problem which is a lack of crafted items on the GTN that are blue or purple.

BioWare can't possible be shocked that there's not more crafted gear on the GTN when the current RE system doesn't lend itself to being cost effective - or helping maintain one's sanity.

The math is utterly irrelevant - the experience isn't working out in reality.

Once you take into account the resource gathering mission's ineffeciencies (relogging 2, 3 times to finally get a T6 Abundant or even Moderate resource that I need), T6 being limited to Abundant missions - further reducing cost effectiveness - the equaiton worsen's further.

I'm all for temporary stims, buffs and a sliding scale, but the straight 20%\10% is just not feasible - economically or TIME wise - for me - and it's definitely not working out - and I'm sitting on on of the consistently heavier load servers. I would also be for taking out all the extraneous gear (Huttesse this, Corellian that) - push it into the vendors as a stop gap and get the clutter out of the GTN - with the exception of purple\orange drops.

Cerion's Avatar


Cerion
05.14.2012 , 04:41 PM | #29
Quote: Originally Posted by venomlash View Post
OP, please read up on cumulative probability. Sure, having failed 30 times doesn't make the next attempt more likely to succeed. But failing many times in succession is very very unlikely.
<sigh> yes, per individual it is unlikely...but in a large population of crafters such as in SWTOR, you will most certainly have a population of players who experience these streaks of bad luck.

It is unlikely that you, yourself, will win the lottery with a 1 in 200,000,000 chance. But yet some always does. The population size dictates that someone will in fact win. The same is in play here. Yes, the odds of fail streaks are are really low. But it is certain to happen to someone.

The only events I've seen in these threads that seem really wonky are the 100 fail streak for the Rakata epic relic. Someone else is closing in on that fail streak as well. That's a 1 in 80,000,000 event. If the population of SWTOR were 80,000,000 players, then you might expect such an outcome.
Good will always triumph because Evil is lazy.

Ironcleaver's Avatar


Ironcleaver
05.14.2012 , 04:48 PM | #30
Quote: Originally Posted by Cerion View Post
Except that he entered the wrong parameters into the calculator. See my follow-up post.
Well, I feel I entered the data correctly, it was pretty straight forward afterall - perhaps i didn't, so i will yield. Being 4am and math not being my strong area I am prone to mistakes since i am human afterall.

That all said.. No matter what formmula is used on the thread here almost all of them are agreeing that given roughly 25 attempts at a 20% success rate, there is going to be a probability of success of 98~99.9999% within those 25 attempts.

This however, dose not match up on how the game "feels". I am a bit bias since I have personally had to RE close to 400 items (from blue to purple) to receive the schematic I was after. This accounts for receiving schems I had no use for.. I know the count was high becasue it took me well over two weeks to finally get the schematic (yeah Im casual).. Every day or so i'd log in and RE everything.. nothing.. Set my crew up to craft 25 more in a single shot - log back in the next day. On average (since I did not keep detailed logs.. how dose? no one..) it took roughly 75 attempts to pop one purple, and it was always the one I didn't want.

I'm glad there are people that have never had to RE more then 25 items to get the schem they were after but I have to call BS myself - every crafter Ive spoken too has had serious issues. Also keep in mind numbers were tweaked with patch 1.2 so it is a pinch rarer now but it can still happen and has. Flawed machenics, that's what it feels like.

It could be as simple that their "random" seed for the RNG system is a pinch flawed. Heck, most people don't even know that if you do not change your "ramdom" seed as a programmer, the numbers will be identical if called twice or more in a row - that's not random at all.

Unknown questions before we start calling anyone "liers" here... (but to ask only a few unknowns, the list could be much larger)
  • When is a new RNG seed called (in the timeframe for REing items)?
  • What is the seed using as it's "random" source (I hope to god not just the system clock)?
  • Is the seed result rounded in anyway shape or form?
  • Is the RNG seed result working within it's expected parameters (small sample and large sample)?
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