Re: measuring distances in grid space

j.Maxwell Legg (
Sun, 30 May 1999 00:58:49 +1200

Tony Downing wrote:
> Now J. Maxwell Legg has written that Patrick Slater developed a routine
> along these lines for Ingrid, but he refers to it as probabilistic. I
> don't see what can be probabilistic about it, once you've got the factor
> scores (which, e.g., Minitab would give you). (This no doubt shows my
> ignorance, but it seems to me that it's as deterministic as you'd expect
> from Pythagoras!)

Chris Evans has written that "It's the Euclidean distances divided by
the 'expected' distances. This serves to correct the values to take into
account the number of elements and (I think) their deviations from the
construct means, i.e. to correct somewhat for the rating scale and how
it is being used by the person (I think!)."


I was referring not to the distances between points which are plotted
from the resultant PCA loadings but the above corrected distances
between the original ratings of the elements on each construct as used
as input into the PCA routine instead of using standard correlations.
There is a marked difference in the quality of the results produced by
WinGrid and other programs because of this.

The probability that I was referring to earlier is the theoretical
accuracy of a routine that "corrects somewhat for the rating scale and
how it is being used by the person". (i.e., there is special handling to
clip for negative distances, e.g., Slater's corrections take into
account inadvertent pole reversals, etc.)

Members on this list should try sometime to review the WinGrid source
code. Now, I understand those on a non Windows PC obviously can't hack
it into a running program but they can still use a word processor to
understand the code and need only ask me to send the required format. To
non programmers this must seem like a daunting task. In reality the code
is a much simpler language than using correspondence to convey meaning.

The fact that my introduction to Patrick Slater was through code and not
correspondence probably accounted for a greater clarity of vision than
would otherwise have been the case. It was my insight into his genius
that prompted me to instruct my managing director to conduct the
purchase of the Ingrid program and the Ingrid name. Because of his
frailty and age, I had Patrick flown out to New Zealand in a first class
state. He was introduced to national television and put up in
comfortable surroundings where we were able to talk at length.

In fact I never had any correspondence with him and all our discussions
were face to face. These discussions when later relayed to a list such
as this may seem a bit 'gob smacking' but that is the nature of
speculative conversation. I regret and wish to reverse any naive
assumption one might have that they don't have the wit to follow such