The sampling errors of maximum likelihood estimates
of item response theory parameters are studied
in the case when both people and item parameters are
estimated simultaneously. A check on the validity of
the standard error formulas is carried out. The effect
of varying sample size, test length, and the shape of
the ability distribution is investigated. Finally, the effect
of anchor-test length on the standard error of item
parameters is studied numerically for the situation,
common in equating studies, when two groups of examinees
each take a different test form together with
the same anchor test. The results encourage the use of
rectangular or bimodal ability distributions, and also
the use of very short anchor tests.
Wingersky, Marilyn S & Lord, Frederic M. (1984). An investigation of methods for reducing sampling error in certain IRT procedures. Applied Psychological Measurement, 8, 347-364. doi:10.1177/014662168400800312
Wingersky, Marilyn S.; Lord, Frederic M..
An investigation of methods for reducing sampling error in certain IRT procedures.
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