Re: Help - Anybody in Edinburgh (and admin!)

Rob Adelman (
Mon, 5 Jan 1998 17:14:47 -0600

Hi Devi,

I would be interested in the Keen article and the Slater article (if it can
be found).
Incidentally, I've come across some data on randomly generated grids I
think in Feixas et al. (1992) or perhaps it was Rathod '74 or thereabouts.
The point was made that random grids lack structure and therefore almost
never resemble the grids
modeling the construct systems of self-organizing agents/persons.

I hope the discussion of qualitative vs. quantitative/ statistically valid
continues as I am struggling with some of these issues myself at present.
Thanks for the lively debate.


Rob Adelman 600 E. Corsicana St., Athens, Tx. 75751, USA
> From: Devi <>
> To: Chris Evans <>;
> Subject: Re: Help - Anybody in Edinburgh (and admin!)
> Date: Monday, January 05, 1998 7:11 AM
> Happy New Year to All!
> Chris Evans responds to my ramblings about personal judgement (is that
> the same as "subjectivity"?!) in factor analysis in an interesting item
> which gives a v.handy reference to Horn (1967): thanks v. much, will get;

> and goes on to say:
> <snip>
> > The Horn paper is actually a rather silly way of
> >making Devi's point, particularly as the diagnostics I was wondering
> >about really ought to have gone some way to diagnosing that the
> >"data" were random. However, I thought it would amuse you all and
> >send it as a bizarre seasonal greeting.
> <snip>
> This prompts the thought that knowing the "random-data" characteristics
> of any computational procedure can be fruitful at times. My brain is too
> fuddled with the shock of returning to work that I can't think through
> the similarities between this and all the stuff I know (not a lot) on the

> way we use sampling distributions to make inferences- I suspect there's a

> great deal of similarity, as Chris' reference to "diagnostics" hints- but

> his reference prompts me to ask about another.
> When doing a Principal Components analysis ofan n x m grid, and making
> judgements about variance proportions accounted for, it is useful to
> know what the PC structure of any n x m sized randomly generated rating
> grid might look like. Patrick Slater once provided a procedure for doing

> just that, but the reference is very obscure.
> Slater, P. (non-dated) "The reliability and significance of a grid"
> internal mimeo, St. George's Hospital, London.
> I wonder if anyone who was in contact with him at the time, (Chris, were
> you at St. George's then? Mildred Shaw, are you there?), early 1970s I
> should think, would have a copy?
> Searching through my box-files to try and find my copy (no luck) I came
> across an item highly relevant to this discussion.
> Keen T.R. "Rotating factors in repertory grid analysis" A paper given at
> the 4th International Congress on PCP, Toronto, Canada, May 1981; mimeo
> Barbican Research group, Garnett College.
> In it, he asserts, with some compelling empirical dat, that the type of
> factor rotation one uses makes a much bigger difference to the factor
> structure as interpreted, than does the type of principal components
> algorithm used in the first place.
> If anyone is interested in the latter, please e-mail me your snailmail
> address and I'll send you a photocopy.
> Cheers,
> Devi Jankowicz