For Mary With The Master In Statistics



she is going to bite. but I am sure you are dieing to ask the question. and hey I am hoping it's a zinger, so please don't disappoint me. 


Let me guess the question  "I had s_x with man A and man B. What is the chance that man A is the father of my baby? 


DANG IT K! I am waiting for Carrie to respond, although that one did get a chuckle. 


Ok, here I am ... be gentle. 


Whew hoo Mary's here! Have you p__sed anyone here off lately? Or have I gotten worked up for nothing? 


I am not sure, sometimes I do, but then I use my alter ego name: Shannon. :) 


Kind of like that.. Actually, I have a very good friend who was raped and has ended up pregnant. She had s_x with her fiancee just the day before. We have been trying to get this figured out because she is considering terminating. Here is my question: The withdrawal method is 80% effective, meaning 20% who use this method get pregnant within the first year of use. 85% of couples who use no method or protection get pregnant within the first year. So a__suming that a woman has s_x in both of these ways on a FERTILE day, what is the actual chance percentage of getting pregnant by each way? Not after a year of use, but as two single s_x acts? I know, of course, that it's impossible to know for sure, but it would just be nice to know the probability. 


oh, and before anbody asks.. she says she did not take the morning after pill because she wasn't in the right frame of mind. It took several days before she told anyone. 


I do not have a masters in stats but I can help you with part of this, I think. The probability for your friend is the same as the general population. For every 100 women that have unprotected, full intercourse during the fertile time, the chance for conceiving is 25% (each fertile period). 1 in 4 women will concieve given all four women have intercourse during their fertile time in a single month. So, who withdrew and who did not? 


Also, I think this falls under "independent" events as far as stats go  Independent Events  Two events are independent if the occurrence of one does not change the probability of the other occurring.  An example would be rolling a 2 on a die and flipping a head on a coin. Rolling the 2 does not affect the probability of flipping the head. If events are independent, then the probability of them both occurring is the product of the probabilities of each occurring.  Specific Multiplication Rule  Only valid for independent events  P(A and B) = P(A) * P(B) 


Carrie, I do not think that the standard probabilties will work in this case. I am not sure you know about sperm behavior in the womb, so let me explain. Studies made show that if 2 different sperm (from different men) are introduced in the womb they will fight for the right of fertilization all the way to the egg. The studies show, no kidding, rivalry between the different sperms. It seem to be a "surviror of the fittest" type of thing. Therefore, it would be hard to know which sperm won. If it was a matter of statistics only, this is a case of sampling with replacement, so the probabilties do not change as you move forward in time (towards the year), they remain the same for one time doing it than for doing it 100 times. In general, you are 65% more likely to get pregnant through full exaculation when compared to a pull out method for every single time s_x happens. But like I said, there is no way to rely on t he stats because of the sperm behavior in the womb. The only way to know for sure is to get DNA from the baby (it can be done before it is born, at as soon as 12 weeks) and compare it to the fiancee. 


^can always count on that! its ok if you don't know everything. Mary what do you think? 


Nice:) I never did well in stats! 


Wait, I thought she was asking something else. Mary, are you sure there is no way to determine a probability for getting pregnant each way? She was not asking who the likely father is, but the chance of getting pregnant each way? It seems like there would be a definite stat for that. Did I fall off my rocker and bump my head? 


enough already. thanks mary 


^ geesh some of you are rude! This is an open forum and alot of people are interested in helping others! Dont be so ignorant. Most of us are here to help but many seem to be here to act snotty and put others down. Its okay if YOU know nothing! Just admit it. You come here to pick on people who try to help. It makes you feel bad that you cant help or dont want to help. 