[Rasch] Noise in observations ...
Lang, William Steve
WSLang at tempest.coedu.usf.edu
Sun Nov 4 22:45:43 EST 2007
Should we suggest, as in physics, the Heisenberg uncertainty principle? Do items (as observation/measurements) have limits to EVER precisely observe the construct "perfectly"?
Without reverting to skinning Schrodinger's cat, I still wonder if CTT would ever have developed the tool kit to explain measurement as well as Rasch? Perhaps, as Paul suggests, CTT may have developed stronger methods if someone had not been wasting time on "IRT".
On the other hand, the question of better tools would likely never even have been asked if Ben had not written, "The truth is that the so-called measurements we now make in educational testing are no damn good!". The historical evidence is not speculative. Rasch has improved our measurement and continues to develop as a viable model today.
The economic decision of which bathroom scale is the best buy is a different issue.
University of South Florida
From: rasch-bounces at acer.edu.au on behalf of Mike Linacre (RMT)
Sent: Sun 11/4/2007 1:56 AM
To: rasch at acer.edu.au
Subject: [Rasch] Noise in observations ...
Paul remarks: "... can only be measured if their observations contain
sufficient noise ..."
Of course, as scientists, we endeavor to reduce irrelevant noise in the
observations in the same way as nuclear physicists do in their experiments
in Quantum Mechanics. But we don't trust only one observation, or
observations that are too close in agreement (recognized as the
"attenuation paradox" in classical test theory or "wood-shedding" in the
We are in the same position as historians:
"When considering an accumulation of evidence, the more randomness in minor
details, the stronger the sense of historical truth."
Gerd Theissen, University of Heidelberg, 1994 (lecture given at the Luther
School of Theology, Chicago).
We are looking for locally-independent sources of information about our
latent variable, in the same way that historians look for
locally-independent accounts of historical events.
Editor, Rasch Measurement Transactions
rmt at rasch.org www.rasch.org/rmt/ Latest RMT: 21:1 Summer 2007
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