On 17 Jan 2001 01:49:33 GMT, Elliot Cramer <[EMAIL PROTECTED]>
wrote:
>There seems to be some confusion about what regression to the mean
>means. Noone is penalized (or advantaged) because of regression to the
>mean. You ALWAYS have RTM in a population whether everyone improves or
>gets worse. It is a property of standardized scores only for a
>population. The simplest explanation is in terms of the regression
>equation for standardized scores
>
>E(z2) = rz1
>
>For positive r<1 if you select individuals with a given z1, their average
>z2 will be smaller than z2 (in absolute value)
>
>Thus Galton found that the offspring of his geniuses regressed towards
>mediocrity. He apparently thought it was a law of nature rather than a
>law of statistics. If he had studied the feeble-minded we would not have
>a technique called regression analysis
OTOH, assuming Galton had used a subject set from a different locus on
the IQ scale: if these so-called mentally challenged subjects
reproduced themselves, their offspring might indeed tend to move
toward the mean, i.e., higher on the IQ scale, right? Would this not
be the same as the offspring of either the very tall or the very short
among us moving toward an arithmetic average? Is it inconceivable
that a pair of dullards could produce a Beethoven or a Fermi for
example? Frankly, I believe old Sir Frances was on to something here.
:-)
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