On Monster Power 1, the drop rate for each key 10%. If I do 10 runs, the chance of having one key dropped in these 10 runs is
1-(1-10%)^10, or about 65%. After getting 3 keys, I can try to get a loot from a uber with a chance of 10%. I will need 3 loot from uber bosses to craft one ring. How do I calculate the Expected Value of total number of runs I will need?
Edit: from wikipedia, I just learned the Mean of a Geometric Distribution is 1/p. So the Expected Value of getting a key drop on Monster Power 1 should be 10 runs. But then, if 10 is the mean, why would
1-(1-10%)^10 ~= 65%?