If you count people passing by you, and first 100 are all men, what is... - XP Math - Forums

 XP Math - Forums If you count people passing by you, and first 100 are all men, what is...

 07-17-2007 #1 Alexander Guest   Posts: n/a If you count people passing by you, and first 100 are all men, what is... ...probability that 101th would be woman? Snoy:If a father has 100 sons in a row,then almost certainly there is somethingwith his DNA that makes female fetusesalmost unviable.
 07-17-2007 #2 morningfoxnorth Guest   Posts: n/a You are at a men's club. The probability that the next person is a man is at least 98%.
 07-17-2007 #3 marvin0258 Guest   Posts: n/a The probability is the same on matter how many men you counted, it could be ten thousand. There is a 50% the next person you walk by is a woman. (Unless your in some space completely dominated by men) But assuming that your in an open space with the population relatively half men half women the probability is 50%. Just because the first 100 are men doesn't mean the 101st with be a man. Likewise just because you've seen a hundred men walk by you doesn't mean that then 101st must be a woman.
 07-17-2007 #4 pki15 Guest   Posts: n/a 50%, the first 100 events are independent of the last event.
 07-17-2007 #5 heidegger_001 Guest   Posts: n/a I think probably about 50 percent because 100 is small number compared to 6 billion people in the world. I'm not sure about the ratio of men to women though.
 07-17-2007 #6 chipmunkian Guest   Posts: n/a Assuming that men and women are 50/50, then the odds would be 1-in-2. The odds do not change for each individual event regardless of what has happened before,
 07-17-2007 #7 Lobster Guest   Posts: n/a It is definitely not 50%. The odds of 100 men passing by you with 50% odds is 2^100 and that is too much of a long shot to dismiss as chance. There is no way to tell the exact odds without more details but I would estimate a 1% chance of seeing a woman.
 07-17-2007 #8 Snoy Guest   Posts: n/a Actually, the probability is indeed 50%. The question does not say "passing by you at a men's club". And similarly, if you have (however unlikely) 100 children, and they are all male, the probability that the 101st child is a female is STILL 50%.There are two options, male or female. Always 50% in generic cases such as this one.
 07-17-2007 #9 bretty418 Guest   Posts: n/a Depends where you are.In Saudi Arabia, a woman can't go out alone.So it's all relative.
 07-17-2007 #10 Dr D Guest   Posts: n/a If you say the answer is anything other than 1/2, it's because you are making up details as you go along.Some answerers above say that if they see 100 men, then it's a strong indication that a lot of men are present. Another person would say that if they see 100 men pass by, there can't be too many left. Without details, the answer is 1/2.RE: Lobster's answer.I agree that if 100 men pass by in a row, the prob of that = 0.5^100. But if 50 men and 50 women pass by in an alternating fashion (M-W-M-W...), the prob of that is also 0.5^100.

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