Rich Ulrich <[EMAIL PROTECTED]> wrote:
> On Thu, 29 Mar 2001 10:17:09 +0200, "Nicolas Voirin"
> <[EMAIL PROTECTED]> wrote:
>> OK, thanks.
>>
>> In fact, it's a "visual" method to see a set of points with the better
>> view (maximum of variance).
>> It's like to swivel a cube around to see all of its sides ... but this
>> in more than 3D.
>> When I show points in differents planes (F1-F2, F2-F3, F2-F4 ... for
>> example), I make rotations, isn't it ?
> I think I would use the term, "projection" onto specific planes, if
> you are denoting x,y, and z (for instance) with F1, F2, F3 :
> You can look at the <projection onto the> x-y plane, the y-z plane,
> and so on.
> Here is an example in 2 dimensions, which suggests a simplified
> version of an old controversy about 'intelligence'--
> tests might provide two scores of Math=110, Verbal= 90.
> However, the abilities can be reported, with no loss of detail, as
> General= 100, M-versus-V= +20. Historically, Spearman wanted
> us all to conclude that "Spearman's g" had to exist as a mental
> entity, since its statistical description could be reliably produced.
And Thurstone's dissatisfaction with Spearman's theories led him to invent
the technique of axial rotation, particularly the varimax criterion
(rotate the axes until the variance of the items' projections on the axes
is maximized). See Stephen Jay Gould's _The Mismeasure of Man_ for more
details; note that Thurstone adopted varimax rotations because their
results were consistent with *his* pet theories about intelligence.
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