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