Expected a posteriori (EAP) estimation of ability,
based on numerical evaluation of the mean and
variance of the posterior distribution, is shown to
have unusually good properties for computerized
adaptive testing. The calculations are not complex,
precede noniteratively by simple summation of log
likelihoods as items are added, and require only
values of the response function obtainable from
precalculated tables at a limited number of quadrature
points. Simulation studies are reported showing
the near equivalence of the posterior standard
deviation and the standard error of measurement.
When the adaptive testings terminate at a fixed
posterior standard deviation criterion of .90 or better,
the regression of the EAP estimator on true
ability is virtually linear with slope equal to the reliability,
and the measurement error homogeneous,
in the range +- 2.5 standard deviations.
Bock, R. Darrell; Mislevy, Robert J..
Adaptive EAP estimation of ability in a microcomputer environment.
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