Re: IQ and Testosterone?

Stephen Barnard (
Mon, 02 Sep 1996 16:42:41 -0800

Stephen Barnard wrote:
> Larry Caldwell wrote:
> >
> > Yep, the tortoise wins every time, right? In fact, you are falling into
> > a common fallacy. Probabilistic information about a population is only
> > valid if you have a statistically valid sample. An individual is not
> > a statistically valid sample. Therefore, statistical information about
> > a population conveys no information about an individual. I know, I
> > responded the same way when I first studied statistics. There is a
> > mind set that automatically leads to generalization and prejudice, but
> > it is wrong. I'm not just talking morally wrong, I mean it gives the
> > wrong results.
> >
> It goes without saying that you need a reasonable sample size to draw
> statistically significant conclusions. Actually, I don't know whether the
> MRI data amounts to a large enough sample size, so you may well be right
> about that. You seem be be claiming, however, that statistically valid
> inferences based on large sample sizes give no (probabilistic) information
> about individuals the population from which the sample is drawn. That is
> incorrect.
> Steve Barnard

I just want to add an example here to clarify what I mean.

Statistics show that male teenagers are far more likely to have automobile
accidents than, for example, women over the age of forty. Therefore insurance
companies charge *much* more to insure a male teenager than they charge to
insure his mother. They are making a perfectly understandable judgement that
the teenager is more likely to be an unsafe driver than is his mother. This is
what actuarial science is all about. It extends to every kind of insurance --
life, medical, accident, whatever. The result is that actions are taken with
respect to individuals based on statistical information.

There are many other arenas in which more or less the same thing goes on --
compiling mailing lists for political contributions, targeted mass mailing,
focus groups, etc.

Steve Barnard