[Rasch] counts to scale conversion

Agustin Tristan ici_kalt at yahoo.com
Tue Jan 24 02:25:45 EST 2006

Hi Tim...it could be nice to have further votes for the three options and see how well this example fits to the person's opinion in this listserve... or how well our opinions fit a model...
  Thank you.

Tim Pelton <tpelton at uvic.ca> wrote:
  What a great example - and starting point for a discussion...

My vote is for option 2.

I think that the phrase in option 3 "...telling us (and the crickets too)..."
demonstrates quite nicely the
limitations of blindly applying an 'ideal' model. Is it reasonable to favor
an elegant theoretical model
that deviates substantially in it's predictions from the observed data when
our lack of understanding of
related factors means that we cannot effectively explain such deviations? Is
it not more appropriate to
choose a pragmatic model (balancing simplicity and accuracy) as an
intermediate model to help us
establish a control or baseline which may then be used to support our search
for other factors?


- >===== Original Message From Agustin Tristan =====
>Hi! I'm trying to follow this topic concerning crickets and scales.
> In abstract: Which is better?
> 1) The simple linear model even if it doesn't fit (the linear model for the
crickets' case).
> 2) Any model who permits us to fit the data (the exp(something) looks to be
like that).
> 3) A theoretical model telling us (and the crickets too) how is the way
crickets should adjust the
frequency of the noise they produce according to temperature...specially if
this theoretical model is
exp(someting) because it looks more interesting or impressive.
> I like Nature and its relationship with math and for me it was interesting
to know that crickets may
use the exponential (even if they don't care about the mathematical
formulation), as well as the seeds in
sunflowers grow exponentially from their center, or the snails grow their
shell, or the ivy plants grow in
an helical 3D curve, or the soil slopes (in soil mechanics) become unstable
and fail according to a
logarithmic spiral, or the growth of populations follows a logistic model, and
so forth... I can also
recognize that I prefer objective items that behave as the Rasch model,
but...I cannot decide in all those
case which is better between (1), (2) and (3)...
> Regards
> Agustin Tristan
>Rense wrote:
>All this illustrates that if we want to stay in business as test gurus then
>we'd better forget about meaningful item hierarchies, sample independence,
>additive measures, and other such niceties. Rather, using methods whose
>results need to be recalibrated for boys, girls, old, and young, ..,
>whatever, ... - and adding a few things like "log(exp(something ...))" to
>our tech reports - should greatly help with job security. :)
>Rense Lange
>-----Original Message-----
>From: rasch-bounces at acer.edu.au [mailto:rasch-bounces at acer.edu.au]On
>Behalf Of Trevor Bond
>Sent: Saturday, January 21, 2006 5:43 PM
>To: Rasch listserve
>Subject: [Rasch] counts to scale conversion
>For all budding scale constructors, this is a hoot:
>check the lovely graphs
>Trevor G BOND Ph D
>Professor and Head of Dept
>Educational Psychology, Counselling & Learning Needs
>D2-2F-01A EPCL Dept.
>Hong Kong Institute of Education
>10 Lo Ping Rd, Tai Po
>New Territories HONG KONG
>Voice: (852) 2948 8473
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Tim Pelton
Assistant Professor
Department of Curriculum and Instruction
University of Victoria
PO Box 3010 STN CSC
Victoria BC V8W 3N4
Phone: (250)721-7803
Fax (250) 721-7598

Mariano Jiménez 1830 A 
Col. Balcones del Valle 
78280, San Luis Potosí, S.L.P. México 
TEL (52) 44-4820 37 88, 44-4820 04 31 
FAX (52) 44-4815 48 48 
web page (in Spanish AND ENGLISH): http://www.ieesa-kalt.com

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