On 24 Jan 2000 14:37:34 -0800, [EMAIL PROTECTED] (Drake R.
Bradley) wrote:
> Rich Ulrich wrote:
>
> > On 24 Jan 2000 09:08:59 -0800, [EMAIL PROTECTED] (Bushaw, Gordon
> > -ADMIN) wrote:
> >
> > > A related question-
> > > I seem to remember reading or hearing that the sex of a child after the
> > > first is substantially more likely to match the sex of the previous child
> > > than not. Does anyone have any information about this, or is it complete
> > > nonsense?
> >
> > It would be complete nonsense if anyone claimed that.
> > But you are probably imagining it.
>
> It is not clear to me why the poster's question is nonsense. He seems to be
> asking whether the outcome of successive births (boy/girl) are independent or
> not. < ... >
Drake,
- I suppose I was taking the question more literally than you are.
He was not asking if the births are independent (which they are). He
was asking if he *might* be remembering some claims, or if anyone had
information, or if it was complete nonsense.
I don't have references; but I remember classroom exercises of obscure
tests to check on any *conceivable* dependency -- it is not like
nobody has every collected this kind of data.
News notes: In yesterday's paper, NY Times, I read about recent
preferences about families in Japan -- formerly, parents wanted sons,
more often than daughters. In recent years, the stated preference has
reversed -- more people tell the pollsters than they want their single
child to be a daughter. If two kids, what is preferred is usually one
of each, but more prefer two girls than two boys. There were various
reasons given: Girls are easier to raise, and don't have as harsh and
fixed a future laid out for them; and parents don't any longer expect
the son to be the main financial support of their own old age.
The preference does not show up in population figures (births), so
far. The article says that abortion is legal for the first 22 weeks
of pregnancy, and that -- to avoid any possible attempts at selection
that way -- their physicians consider it unethical to reveal the
gender of the unborn earlier than that. Other methods of selection
don't work very well.
Younger Japanese, it says, are less impressed than their elders by the
ethics; and more concerned with the technical possibilities. It
described some folk-attempts, and one valid (if you want to go that
far) method: Prior to artificial insemination, sperm can be sorted by
weight in a centrifuge, since sperm with Y-chromosomes generally
weigh less than the X-chromosomes, by the amount of that extra arm.
(It was not in that article, but I think I have read that there can be
70-80% success by that method.)
--
Rich Ulrich, [EMAIL PROTECTED]
http://www.pitt.edu/~wpilib/index.html
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