[Rasch] Noise in observations ...

Mike Linacre (RMT) rmt at rasch.org
Sun Nov 4 17:56:16 EST 2007

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 
legal arena).

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.

Mike L.

Mike Linacre
Editor, Rasch Measurement Transactions
rmt at rasch.org www.rasch.org/rmt/ Latest RMT:  21:1 Summer 2007
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