Originally Posted by JaneQSmythe
This information is actually part of the "informed consent" that everyone is supposed to receive prior to undergoing these procedures - but you hear 99.9% effective and assume it will never happen...to you (although 99.9% means it will happen to 1 in 1000 - and how many people undergo these procedures?). The bottom line "truth" is that there is NO 100% effective birth control...Perhaps, technically, abstinence but, even then, you have to be aware that ejaculation near the vagina can (rarely) result in pregnancy even without penetration.
Humans are inherently terrible at probability. I was talking to a doctor once about an unnamed patient. He explained that the chance of her preemie baby surviving was 40%. She kept trying to get him to tell her whether she was in the 40% or the 60%. He was at a loss. She didn't understand basic statistics. You throw a die, there's a 1/6 chance you'll get a 3. I can't tell you whether you're in the 1/6 or 5/6 until you actually throw the die. Then I can give you 1/1 odds that what you already rolled was a 3 or not.
is why Quantum Mechanics is so hard.