How many polypags would I need to get to have good odds of getting all in the series? Despite helpful prior answers about squeezing polybags to determine contents, the new Unikitty! series seems pretty immune to this sort of the effort since all of them are in one of 3 shapes and there are inner bags which make it even harder to feel the parts.  So I bought a bunch of polybags from two different stores in the same town.  After buying 25+ polybags I'm still 5 short of the set.  Is it just bad luck or is my guess of the odds that far off?
It's known as the "Coupon collector's problem". To get all 12 you would on average need to buy 38. Buying a whole box (or finding someone who did and buying a set from them) seems like a much more attractive solution.