ESTIMATION OF ITEM RESPONSE THEORY MODELS WHEN ABILITY IS UNIFORMLY DISTRIBUTED

Yıl 2017, Cilt: 7 , 30 - 37, 04.08.2017

Tugba Karadavut

Öz

Item
Response Theory (IRT) models traditionally assume a normal distribution for
ability. Although normality is often a reasonable assumption for ability, it is
rarely met for observed scores in educational
and psychological measurement. Assumptions regarding ability distribution were
previously shown to have an effect on IRT parameter estimation. In this study,
the normal and uniform distribution assumptions for ability were compared for
IRT parameter estimation, when the actual distribution was either normal or
uniform. Uniform distribution assumption in
2PL model yielded more accurate estimates of ability independent of the actual
ability distribution. Similarly, a uniform distribution assumption for ability
yielded more accurate estimates of ability in 3PL model when the actual ability
distribution was uniform. For Rasch model, there was not an explicit pattern
for comparing accuracy of ability estimates from uniform and normal
distribution assumptions.

Anahtar Kelimeler

Item response theory, IRT, uniform distribution, normal distribution, ability

Kaynakça

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