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View Full Version : Booster to Primal ratio - how does it work?



Bells
05-01-2014, 10:14 PM
This is a thing i haven't been able to find out yet by poking around, if there is a discussion on that, please point it out, thanks.

each time you purchase packs, there is a chance of getting primals... but... is it per purchase or per pack?

Like, considering the Primal chance comes at the roll of a dice. I buy 20 packs in one go... do i get 1 roll of the dice on my 1 purchase of 20, or do i get 20 rolls of the dice from my 20 packs in 1 purchase?

i bought 55 and then bought 15 and i got 1 primal, which i'm ok with ... so i wanted to understand the mechanics behind it.

Gorgol
05-01-2014, 10:19 PM
every pack is a roll. bulk purchase or single purchase makes 0 difference.

hex_colin
05-01-2014, 11:00 PM
You have a 2% chance every time you get each Booster from CZE at the point it hits your inventory. Notably, that means that even if you buy 50 boosters, you actually have a ~36.42% chance of not seeing a primal. Over time, and with enough pack purchases, you'd see your actual rate approach the 2% chance.

Edit: Added math...

The formula to calculate your Primal chance given a drop rate ( x ) over any given number of booster purchases ( y ) is this:

1 - ( ( 1 - x ) ^ y )

So....
50 Packs: 1 - ( ( 1 - 0.02 ) ^ 50 ) = 63.58% chance of getting at least one, 36.42% chance that you won't see one
100 Packs: 1 - ( ( 1 - 0.02 ) ^ 100 ) = 86.74% chance of getting at least one, 13.26% chance that you won't see one

Furthermore... there's actually a 4.37% chance that someone getting 155 packs (the most common KS amount) won't see a primal :( So, it sucks when it happens, but it's not actually a crazy rare outcome.

Pretty useful calculator @ http://stattrek.com/online-calculator/binomial.aspx


Probability of Success: 0.02
Trials: Number of Regular Packs
Number of Successes: Number of Primal Packs (1 for the calculations above, but you can put in the number you'd like to see, e.g. 4 in 100 packs, and see what the probabilities are)

Rycajo
05-01-2014, 11:01 PM
As Gorgol said, you get 1 roll for a free Primal for each booster purchased. And CZE is so nice that the Primal is a bonus now, it doesn't even take the place of the booster you purchased.

cferejohn
05-02-2014, 12:17 AM
As Gorgol said, you get 1 roll for a free Primal for each booster purchased. And CZE is so nice that the Primal is a bonus now, it doesn't even take the place of the booster you purchased.

I think that is also to stop drafts from being kind of screwed up (and people being pretty screwed when they buy in to a draft and have "their" primal pack split 8 ways...

Daer
05-02-2014, 07:24 AM
Looking at the probability I'm happy with my 11/155 (not including guaranteed) Primals on a king tier.

hex_colin
05-02-2014, 07:25 AM
Looking at the probability I'm happy with my 11/155 (not including guaranteed) Primals on a king tier.

Yeah, that's insanely good luck! :)

Edit: You're in the 0.0317%!

ossuary
05-02-2014, 07:49 AM
It's the standing record of reported numbers.

Even aside from the fact that you got the most from a single tier, your total is also well above average. You bastard. :)

Xenavire
05-02-2014, 08:10 AM
A guildy of mine got 2/25 primals, with 6 legends from those 25 packs +4 more from the primals. Some people have all the luck haha.