Talk:Ghazt/@comment-12605743-20130718155422/@comment-7326455-20130719065928

Sorry, that's not what I said - what I said was 70 attempts would give roughly a 50% chance of getting one at least once during those 70 attempts. It's binomal theory - mathematically, the chances of at least one success from n attempts when the probability of success is p is equal to (1-(1-p)^n).