[Rasch] counts to scale conversion

Agustin Tristan ici_kalt at yahoo.com
Mon Jan 23 12:07:53 EST 2006


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 <renselange at earthlink.net> 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:
http://www.dartmouth.edu/~genchem/0102/spring/6winn/cricket.html
check the lovely graphs
collegially
Trevor
--
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
Fax: (852) 2948 7983
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