Tuesday, August 24, 2010

What are the chances of a child sharing the same birthday as a parent?

My daughter has the same birthday as I. She came 2 weeks early. All natural, no C-section, no labor inducing drugs. Take into consideration menstrual cycle, day of conception and gestation time. I know that every child has 2 parents and the easy answer would be 1:183 but that is not the right answer. Put some thought and mathmatics into it.





Thanks for your time and efforts.What are the chances of a child sharing the same birthday as a parent?
i dont know. but my stepdad and his sister share the same birthday 4 years apart. they were even born in the same hour.What are the chances of a child sharing the same birthday as a parent?
I have a friend who has the same birthday as her mom and her oldest son.
1 in 365.
There are a lot of other factors, not just mathmatical, that come into play. A due date is merely an estimate, based upon the menstrual cycle, and doesn't clearly indicate that ovulation took place exactly 2 weeks past the first day of the last period. It can generally be 2 weeks before or after the due date and is considered a full term pregnancy. With all of the hormonal and physiological changes in both the mother and baby, really it's a wonder that there can even be a due date.
It actually is 1 in 365.





I have a feeling you're think of the ';birthday paradox';, which says if there are 23 people in a room, the chances are 50% that at least two of them share a birthday, and if 60 are in a room, there's a 99% probability that two people share a birthday.





But you're not talking about the birthday paradox. You're specifying the date (your birthday), AND the other person (your daughter).





The equation is thus: 1- {([365-1]/365) raised to the exponent of ';n';}, which is the number of other people to whom you are comparing birthdays. In this case, 1 (your daughter).





So, the equation becomes 1-{(364/365) raised to 1}


Which is, of course the same as 1-(364/365).


Easily change 1 to 365/365...subtract 364/365 from that...you get 1/365.





Does that help?
conception and gestation time are not exact science, they are more like educated guesses, so that really doesnt help.
1 in 365, leap year changes that but close enough.

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