Hi, this is just a curiosity question which occurred to me when I was reading the Wikipedia page on condoms. I'm sorry to start a topic on something so basic, but there isn't a category on the homework section for "other" aside from calculus/physics ect. Let's say condoms are 98% effective over a year of use in preventing pregnancy. Let's pretend that double-bagging actually increases the effectiveness by adding another 98% chance of effectiveness (in reality, this appears to be untrue). How is that formally done? I was thinking that 98/100 of the times, pregnancy would not happen. 2/100 times it would. Since it is double-bagged, 98% of those 2/100 would not happen. That means .98 * 2 = .0196 or 1.96%. In other words, 98.04% of those using double-bagged condoms would have no pregnancies. Is that right -- would it increase the chance of no pregnancies .04%? It just seems like such a small difference.