Poem: What is Rasch?

Rasch is a model of probability
that estimates person ability,
that estimates item difficulty,
that predicts response probability
nothing but a function of ability and difficulty.

Rasch is a model of uniformity
that places the values of person ability
and the values of item difficulty
on the same scale with no diversity.

Rasch is a model of sufficiency
that uses number right for estimating person ability
and count of correct responses for item difficulty;
that relates raw score to person ability
and response distribution to item difficulty
-- with no ambiguity.

Rasch is a model with invariance property
that fosters person-free estimation of item difficulty
and test-free estimation of person ability;
that frees difficulty estimates from sample peculiarity
and ability estimates from difference in test difficulty.

Rasch is a model with diagnosticity
that flags items away from unidimensionality,
or items with local dependency;
that identifies persons with response inconsistency,
or persons or groups measured with inappropriacy;
that maintains construct fidelity and enhances test validity.

Rasch is a model of ubiquity;
from educational assessment to sociology,
from medical research to psychology,
from item analysis to item banking technology,
from test construction to test equity ....
-- nothing beats its utility and popularity.

Huixing Tang

Tang H. (1996) What is Rasch? Rasch Measurement Transactions 10:2 p. 507.

What is Rasch? Tang H. … Rasch Measurement Transactions, 1996, 10:2 p. 507

Rasch Publications
Rasch Measurement Transactions (free, online) Rasch Measurement research papers (free, online) Probabilistic Models for Some Intelligence and Attainment Tests, Georg Rasch Applying the Rasch Model 3rd. Ed., Bond & Fox Best Test Design, Wright & Stone
Rating Scale Analysis, Wright & Masters Introduction to Rasch Measurement, E. Smith & R. Smith Introduction to Many-Facet Rasch Measurement, Thomas Eckes Invariant Measurement: Using Rasch Models in the Social, Behavioral, and Health Sciences, George Engelhard, Jr. Statistical Analyses for Language Testers, Rita Green
Rasch Models: Foundations, Recent Developments, and Applications, Fischer & Molenaar Journal of Applied Measurement Rasch models for measurement, David Andrich Constructing Measures, Mark Wilson Rasch Analysis in the Human Sciences, Boone, Stave, Yale
in Spanish: Análisis de Rasch para todos, Agustín Tristán Mediciones, Posicionamientos y Diagnósticos Competitivos, Juan Ramón Oreja Rodríguez

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