Probability - Contraception With a perfect use of the condom you have a 2% chance to get pregnant each year. These figures seem surprisingly high to me. So I was wondering **what the chance is to have a baby after a lifelong use** (let's assume 25-35 years). What if you use the pill? And with both the pill & condom? What with the "typical use" scenario? Pregnancy chances after one year of use: * Pill | Perfect use: 0.3% * Pill | Normal use: 8% * Condom | Perfect use: 2% * Condom | Normal use: 15%

If you have a probability of failure for one year of $p$, you have a probability of no failure for one year of $1-p$. Then the chance of no failure for $n$ years is $(1-p)^n$ if you assume the chances are independent.