Look up the topic regression to the mean. This means that of values
measured several times , when extremes are revisited they can be at a
more typical value.
In article <8itf0t$a68$[EMAIL PROTECTED]>,
Gene Gallagher <[EMAIL PROTECTED]> wrote:
> Rich Ulrich wrote:
> > These are not quite equivalent options since the first one really
> > stinks -- If you are considering drawing conclusions about
causation,
> > you need *random assignment* and the two Groups of performance are
the
> > furthest thing from random.
> >
> > Let's see: the simple notion of regression-to-the-mean says that
the
> > Best performers should fall back, the Worst performers should
improve;
> > that's a weird main-effect, which should wreak havoc with
interpreting
> > other effects.
> > Or: If the Pre is powerful enough to measure potential, then a
> > continued-growth model says that Best performers should improve
more,
> > even given no treatments.
>
> This pattern was described in an obit about two-three years ago in the
> NY Times. A statistician's obit noted that he'd found a flaw in the
> Israeli air force's training program. Apparently, the Israeli air
force
> was punishing the worst performers in a test because this usually
> produced a better performance in subsequent tests and was supposedly
> much more effective than positive reinforcement. They'd found that
> positive reinforcement of the best performers often resulted in a
poorer
> performance on the next test. This now-deceased statistician pointed
> out the confounding effect of regression to the mean on this
assessement
> of negative and positive reinforcement. The effectiveness of negative
> reinforcement (punishment) could be nothing more than a chance effect.
>
> I wish I had the citation for the study or the obit.
>
> Does anyone else in the group have a citation of this study?
>
> --
> Eugene D. Gallagher
> ECOS, UMASS/Boston
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
>
Sent via Deja.com http://www.deja.com/
Before you buy.
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