Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: The "two child problem"



John Mallinckrodt asked our opinion about the "Ask Marilyn" column in the
last "Parade".

I agree with Marilyn, but I haven't spent a large amount of time considering
the issue, and haven't looked up the original column which precipitated the
uproar, so I might be wrong due to some unforseen complication that I have
not considered.

The way I see it, of the catagory of two-child parents there are the
following possible approximate probability distributions of genders:
1/4 with two girls, 1/2 with one boy and 1 girl, and 1/4 with two boys.
Therefore, of the 3/4 which have at least one boy there are 1/3 = (1/4)/(3/4)
of them with two boys. Thus a mother with two children has a conditional
probability of 1/3 of having both of them as boys *given the condition* that
at least one of them is a boy.

David Bowman
dbowman@gtc.georgetown.ky.us