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The "two child solution"



It will be convenient to my argument to assume that Donald's two
ex cathedra assertions (quoted below) are false.
That is to say:
1)Twins are not universally given serial birth times.

2)Ms. V Savant may possibly have been concerned with the very real
sex-linked differential mortality rates with the more numerous male babies
perishing
initially at a higher rate than girls -
she may have considered the inferior neo-nate survivability in the US
compared for example with Western Europe.
Who knows, she may even have paused for a moment to recall that US
citizens have shorter lifetime expectancies than Europeans...

With these facts in mind, let us begin.

For the hypothetical father, whose situation is set in the (hypothetical
future-present) tense, so that we are forced to consider prospective
probabilities...
....the birth sequence is here evidently to be considered sequential
with a son first, and so we are left with just three possibilities;
a junior son, a junior daughter, or a sole survivor of a multiple birth.

For the reason already mentioned a son is slightly more likely than a
daughter,
however, the sole survivor of a multiple birth would have a slight bias in
favor of the girl - as being a more robust neo-nate, statistically.

Unfortunately this female survival advantage only has a small probability
of eventuating - twin births comprising a still-birth and a live-birth are
rather rare. The overall effect is for the hypothetical father to have
boys in slightly LESS than the usual statistical proportion for boy vs. girl.

For the hypothetical mother, we are led to consider more eventualities;
for each birth:
a son, a daughter, a multi birth sole survivor, a twin or an identical twin.

If the first offspring is male, the other could be female with slightly
smaller probability, or the other a twin of male or female gender, or
another identical male with small probability.

I'm sure that you can see the general picture:
the probabilities are quite narrowly divided as between the prospective
father and the prospective mother with one distinctive difference:
because surviving twins are not ruled out for the mother, and we know that
one offspring is a boy, we acknowledge that the small possibility of a
second identical twin boy is enough to tip the balance in her favor - that
is; she is slightly more likely to have two boys, so long as we do not
postpone this observation too late into the lifespans of the male
offspring, who suffer increased mortality versus the girls.

Regards
brian w



At 16:46 7/28/97 -0400, you wrote:
....

Even in the case of twins, one is always recorded as being born first.
Also, I'm sure Marilyn wasn't concerned with the slight difference in
male/female birth rates, which, in this case, wouldn't be enough to affect
the conclusion she specifically asked for.
.....
Dr. Donald E. Simanek
******************************************************
....
On Mon, 28 Jul 1997, John Mallinckrodt wrote:

A man and a
woman each have two children. The man's older child is a son and at
least one of the woman's children is a son. Is either more likely
than the other to have two sons?

A. John Mallinckrodt

*******************************************************


brian whatcott <inet@intellisys.net>
Altus OK