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If you plan to RE X items, how do you calculate the odds you'll get at least 1 schem?

STAR WARS: The Old Republic > English > Crew Skills
If you plan to RE X items, how do you calculate the odds you'll get at least 1 schem?

Felioats's Avatar


Felioats
10.25.2012 , 05:12 PM | #1
I'd like to know because it might help me decide how many items to direct my companions to make before I log off.

I know you don't add the chances together. Reverse engineering two items with a 20% chance to learn a schematic doesn't mean there's a 40% chance. If you flip a coin twice, there is not a 100% chance you'll get at least one Tails.
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Alec_Fortescue's Avatar


Alec_Fortescue
10.25.2012 , 05:25 PM | #2
I don't calculate, I just R/E The more you calculate, the more you hesitate. Keep that in mind.
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http://www.swtor.com/r/FsJS44 - Accept my referral to express gratitude for my years-long fight for iconic Jedi attire in this "Star Wars" game. You'll get some goodies on top of it, too.

Oskie's Avatar


Oskie
10.25.2012 , 08:45 PM | #3
This is a classic statistics type question. You actually need to multiply the chance that you don't get a schematic each time and subtract that from one. So 2 attempts (before the 2nd attempt) you have a 1-(0.8*0.8)=36% chance but after the 1st attempt it is still 20%

Felioats's Avatar


Felioats
10.25.2012 , 09:23 PM | #4
I get it!

n is the number of items being reverse engineered.
d is the chance, as a decimal, that an item will teach a schematic. 10% is 0.1; 20% is 0.2.

1 - ((1 - d) to the power of n) = chance of learning a schematic

So the odds of getting an artifact schematic are:

1 item: 10%
2 items: 19%
3 items: 27%
4 items: 34%
5 items: 41%
6 items: 47%
7 items: 52%
8 items: 57%
9 items: 61%
10 items: 65%
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killahcheese's Avatar


killahcheese
10.26.2012 , 12:32 AM | #5
wow nice calculation.
So is this saying that for ANY item you RE, it increase the chance of getting schematic?

ThatGnome's Avatar


ThatGnome
10.26.2012 , 04:18 AM | #6
Quote: Originally Posted by killahcheese View Post
wow nice calculation.
So is this saying that for ANY item you RE, it increase the chance of getting schematic?
Each time you RE an item, there's a 20%(10%) chance that you'll get the improved schematic. Cumulatively, it becomes more and more likely that you'll have the schematic, but that doesn't increase the chance that it'll pop up this particular time. Sometimes you'll make twenty-four attempts to RE a particular piece of Armouring, still not have it, but it's still only a 20% chance that the next attempt will get it. And sometimes you'll get two in a row, like I did REing a particular type of helmet yesterday.

wainot-keel's Avatar


wainot-keel
10.26.2012 , 07:19 AM | #7
Given the fact that logging/reloggin has become a bit tiresome with all the alts, I like to craft between 5 and 10 items at least, depending on the chance ( 0.2 or 0.1) and depending on the prefix I'm after. For example, if I just got the Redoubt version, I'll make 10 of those to get the Veracity one. If I'm being unlucky and I got all the other prefixes first, I'll make 5.
Ideally, you'd RE 1 by 1 to save mats, but the sense of grind would be too strong and an actual waste of time. I just try to be practical and I don't calculate odds.

Felioats's Avatar


Felioats
10.26.2012 , 07:44 AM | #8
Quote: Originally Posted by wainot-keel View Post
Given the fact that logging/reloggin has become a bit tiresome with all the alts, I like to craft between 5 and 10 items at least, depending on the chance ( 0.2 or 0.1) and depending on the prefix I'm after. For example, if I just got the Redoubt version, I'll make 10 of those to get the Veracity one. If I'm being unlucky and I got all the other prefixes first, I'll make 5.
Ideally, you'd RE 1 by 1 to save mats, but the sense of grind would be too strong and an actual waste of time. I just try to be practical and I don't calculate odds.
Yeah, I decided to do this after I recently got frustrated and just directed my guys to make 15 prototype (blue) items. Then I got the artifact (purple) I wanted on like the second one.

That can still happen knowing this, and I'm not sure how useful it is, but it is nice to know.
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psandak's Avatar


psandak
10.26.2012 , 08:13 AM | #9
Quote: Originally Posted by killahcheese View Post
wow nice calculation.
So is this saying that for ANY item you RE, it increase the chance of getting schematic?
There is a difference between chance and probability. What Felioats is calculating is the probability of success given a specific number of tries.

IMO a better visual is the probability of continued failure versus the fixed chance of success.

For a 20% RE on the first attempt your chance of failure is 80%. Simple enough. Now on the second attempt while the chance of success is still only 20%, the chance of two failures in a row is 64% (80%^2). Continuing the math the probability of...

3 failures in a row is 51.20% (80%^3) compared to 20% chance of success
4 failures in a row is 40.96% (80%^4) compared to 20% chance of success
5 failures in a row is 32.77% (80%^5) compared to 20% chance of success
6 failures in a row is 26.21% (80%^6) compared to 20% chance of success
7 failures in a row is 20.97% (80%^7) compared to 20% chance of success
8 failures in a row is 16.78% (80%^8) compared to 20% chance of success

Basically, if you get a schematic before the 8th try consider yourself lucky because you beat the odds.

on a 10% RE you have to go 21 consecutive failures before the odds tip in your favor. The probability of 21 failures in a row is 10.94% (90%^21) compared to 10% chance of success.

Then you have the law of averages to deal with. Perform millions of REs at 20% and the ratio of successes versus failures will work out to approximately one success to four failures (1:4). Another way to look at it is one in five attempts results in a success. The problem is when someone perform 20 REs at 20% and does not see that 1:4 ratio and they come to these forums to complain about it. They complain about not getting one schematic in 20 attempts but they "conveniently forget" the fact that they got two schematic is three tries a week ago . But this human nature - we tend to focus on the negative .

Arkerus's Avatar


Arkerus
10.27.2012 , 12:05 PM | #10
Quote: Originally Posted by killahcheese View Post
wow nice calculation.
So is this saying that for ANY item you RE, it increase the chance of getting schematic?
No.

Every individual roll is 20%. No matter how many times you did it before, it's only 20% each roll.

You chance, OVER TIME, is increased as odds say eventually you will hit the schematic. However each individual roll is 20% regardless of anything that has every happened before it.


This the classic gambler fallacy.
Hooning in the rex : http://youtu.be/xtXUM6yPMCY