No, she definitely called OP a ****. And I'm pretty sure OP called her a psycho because she lies to her students and insults them when they call her out on it.

This teacher sounds extremely ignorant...

Agreed. She needs to get some as soon as possible.

That's not all all how the probability works. Your (.99)^(365) is the success rate over the 365 trials. For the chance of failure, you'd need to do 1 - (Chance of Success). Regardless, each event is independent, so it's not like prior success makes the next trial more likely to fail.

195 clearly needs to take an elementary statistics class. What a colossal failure. 198 has it right.

198, you seem to have some knowledge, but you’re misinterpreting the result. Yes, I calculated the success rate over 365 trials, which as you seem to agree is 2.6%. That’s your chance of NOT having a failure, hence a 97.4% chance of having one. To really oversimplify it, 99% means it’s good 99 times out of a hundred, so on average you have one failure every hundred times. 1-(chance of success) gives you the fail rate of one percent. .01^365 would give you the chance of every condom failing for the year, ie zero. The point being that while they are obviously vastly safer than bareback, from time to time you will have a condom fail, and it’s only intelligent to consider the possibility. 201, now that you mention it, I just might have had such a class, along the way to my math degree and current career in applied statistical analysis. But I think I learned what 99% means long before that, certainly by middle school. Let’s put this in a context that might not scare you so much. Assume that, on average, 99 out of every 100 African Americans voted for Obama (99%). Now assume you interview a group of 365 African Americans. Since the average for the entire nation is that one in every hundred voted against him, what are the chances you can find at least one in a particular 365 that voted against him?

PS 198, You are right that the chance of any particular use being that failure are only 1%, but if you repeat the trial over and over, the chance of at least one failure out of the total gets uncomfortably high. Would you, for an absurd example, continue to buy milk if you learned that one of every hundred bottles could give you aids? Now that's greatly overstating the case, since obviously everyone does not have an STD and you are unlikely to get someone pregnant from one broken condom. But on average, one of every hundred condoms will fail, and it could be the first one you use. (And that’s if you buy the “99%” stat). A lot of people like to pretend that condoms are some sort of magic device protecting you from all harm. They are not. If you have any kind of regular sex life, you will see the occasional failure. Period. A condom is more like a seatbelt. Yes, the only guaranteed way to never be hurt in a crash is to never go near a vehicle, but very few are going to do that. And wearing a seatbelt does make you much less likely to get hurt in a crash, so you should be taught to wear one when you do drive. But if your driver’s ed teacher, or anyone else, tells you that wearing a seatbelt means you can go 95 mph through a residential zone in perfect safety, they are dangerously wrong. Maybe they are overselling the safety device to convince you to use it, but they have pushed it from being a protection into being an enabler for reckless behavior. A one night stand with a stranger you meet at a bar is always going to be risky. It’s like street racing; exciting, interesting, almost everyone has either considered or done it at least once…but while you’d be stupid to not wear your seatbelt for the street race, you’re even stupider if you think it’s a perfect protection from harm. Might as well push the metaphor to the end. Drive, enjoy it, you can’t really go through life without it. Wear your seatbelt, obviously. But also drive defensive, watch the speed limit, don’t text…etc.