Probability of Drop Chances on Wow Items

[BenVitale]

Drop chance probability

http://www.wow.com/2010/01/13/drop-chance-probability/


For some reason, the explanation provided in that document is not clear to me.

Could anyone offer a different explanation?

 

[EnumaElish]

Tossing a fair coin.

The probability of "heads in the first throw" is 0.5.
The probability of "heads in the second throw" is 0.5.
The probability of "(one or more) heads in the first two throws" is equal to "probability of HH + probability of HT + probability of TH" = 1 - probability of TT = 1 - ("probability of tails in the first throw" times "probability of tails in the second throw") = 1 - (0.5 times 0.5) = 1 - 0.5^2 = 0.75.

Note that if "probability of heads" = x then "probability of tails" = 1 - x. In my example x = 1 - x = 0.5.

 

[BenVitale]

So,

flip But over the course of 100 tosses, the probability of getting heads is way more than 50%. (In fact, the chance is 99.999999999999999999999999999921% that we'll get heads at least once.)

translates into the probability of at least one Heads appears in "y" throws.

In your example y = 2, and we know that x = 1/2