"G. Marc Turner" wrote:
> At 11:53 AM 2/28/2000 -0800, Judith A. Roberts wrote:
> >Where did the mean of 100 and standard deviation of 15 for I.Q. come
> >from? I did not have a clue about this one, and neither did one of the
> >other statistics instructors.
>
> My guess on this would be what Mark (not myself, but the other one) said
> about keeping some consistency with the IQ=MA/CA*100 scoring system.
> However, the issue of not having negative IQ scores is also a contributing
> factor with most standardized scores that get reported to the general
> public (SAT, GRE, etc.) How would you explain to a parent that their child
> had a negative IQ or negative achievement? Just avoid the situation by
> rescaling things to ease interpretation.
I don't think folks are "rescaling" to prevent negative numbers or to avoid
some situation. That strikes me as implying that, once again, statisticians
are somehow arbitrarily manipulating numbers for some "convenience" rather
than for some sound reason. I think most statisticians have better things to
do (and get paid well for it).
In order to get negative numbers with the IQ (Intelligence *Quotient*), one of
the numbers in the ratio would have to be negative. Chronological age, for all
intents and purposes, cannot be less than zero (unless you're referring to
fetal age perhaps... but that could be included in the positive as well,
technically). And mental age of less than zero really wouldn't make sense
either, unless you're referring to some sort of Buddhist pre-life. Neither of
these values makes any sense if they were negative. Therefore the quotient
can't be negative, by definition of the concept, not by rescaling of the
numbers.
Hope this helps.
Cheers,
--
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Steven M. Specht, Ph.D.
Associate Professor of Psychology
Psychology Department
Utica College of Syracuse University
1600 Burrstone Rd.
Utica, NY 13502
(315) 792-3171
*** be fruitfly and multiple
