19 Sisters, 1 Ephemera

[Planetary_Devastation]

5 hours ago, LordLeraje said:

I wish my drop rates were as good as 1/19. Lucky you

 

DE here is my new rule (see I can make them up too) . I will purchase no platinum until I get a sister's ephemera. If you ever want my money again, FIX YOUR DROP RATES!!!!!

All you could ever do is just keep trying and trying, the more you do the more hyped up you get to murder another sister, hopefully getting it, that's how it was for me, good luck 

[(PSN)Pragmatic_2015]

Call it stimulating the in-game economy. Just remember not to be to stingy towards your fellow tenno and always give a fair price.

[(NSW)BalticBarbarian]

15 hours ago, Tesseract7777 said:

What I'd like to see from one of the math nerds is an explanation on what the odds are of actually getting say, 4 ephemera from 20 liches, when those are your FIRST 20 liches. 

There's not much to see there - this is simply the "Binomial distribution" with the right parameters (probability of success p=0.2, look for k=4 successes out of n=20 attempts). We can write pages upon pages on it, but it'll be easier to just read the wikipedia article - it explains things fairly well. The formula you're (technically) asking for - the probability of getting exactly 4 ephemeras out of 20 sisters -  is the probability mass function. Just plug the numbers in and enjoy!

The slight complication is that this is not the number you actually want - you actually want the probability of getting at least 4 ephemeras from rolling 20 (40, 60, 100) sisters. This can be calculated as "1-F(k-1)", where F is the cumulative distribution function. Here you just take 1 and subtract the probabilities of getting exactly 0,1,2 or 3 successes.