Abstract
Estimating ability from items isomorphs. effects on the reliability of the test scores. This article focuses on the errors of the item parameter estimates and their effect on the reliability of the test scores. In particular we consider the errors introduced by the process of creating item isomorphs. The research is conducted by means of a Monte Carlo simulation. The simulation includes several conditions r egarding the size of the errors and the number of isomorphs in the item pool of an adaptive test. The results show that the errors due to the isomorphing process do not compromise the psychometric status of the test scores except in the condition with highest errors.
